littlejs.release.js

// LittleJS - MIT License - Copyright 2021 Frank Force

'use strict';

/** 
 * LittleJS - Release Mode
 * - This file is used for release builds in place of engineDebug.js
 * - Debug functionality is disabled to reduce size and increase performance
 */



let showWatermark = 0;
let debugKey = '';
const debug = 0;
const debugOverlay = 0;
const debugPhysics = 0;
const debugParticles = 0;
const debugRaycast = 0;
const debugGamepads = 0;
const debugMedals = 0;

// debug commands are automatically removed from the final build
function ASSERT          (){}
function debugInit       (){}
function debugUpdate     (){}
function debugRender     (){}
function debugRect       (){}
function debugPoly       (){}
function debugCircle     (){}
function debugPoint      (){}
function debugLine       (){}
function debugOverlap    (){}
function debugText       (){}
function debugClear      (){}
function debugSaveCanvas (){}
function debugSaveText   (){}
function debugSaveDataURL(){}
/**
 * LittleJS Utility Classes and Functions
 * - General purpose math library
 * - Vector2 - fast, simple, easy 2D vector class
 * - Color - holds a rgba color with some math functions
 * - Timer - tracks time automatically
 * - RandomGenerator - seeded random number generator
 * @namespace Utilities
 */



/** A shortcut to get Math.PI
 *  @type {Number}
 *  @default Math.PI
 *  @memberof Utilities */
const PI = Math.PI;

/** Returns absoulte value of value passed in
 *  @param {Number} value
 *  @return {Number}
 *  @memberof Utilities */
function abs(value) { return Math.abs(value); }

/** Returns lowest of two values passed in
 *  @param {Number} valueA
 *  @param {Number} valueB
 *  @return {Number}
 *  @memberof Utilities */
function min(valueA, valueB) { return Math.min(valueA, valueB); }

/** Returns highest of two values passed in
 *  @param {Number} valueA
 *  @param {Number} valueB
 *  @return {Number}
 *  @memberof Utilities */
function max(valueA, valueB) { return Math.max(valueA, valueB); }

/** Returns the sign of value passed in
 *  @param {Number} value
 *  @return {Number}
 *  @memberof Utilities */
function sign(value) { return Math.sign(value); }

/** Returns first parm modulo the second param, but adjusted so negative numbers work as expected
 *  @param {Number} dividend
 *  @param {Number} [divisor]
 *  @return {Number}
 *  @memberof Utilities */
function mod(dividend, divisor=1) { return ((dividend % divisor) + divisor) % divisor; }

/** Clamps the value beween max and min
 *  @param {Number} value
 *  @param {Number} [min]
 *  @param {Number} [max]
 *  @return {Number}
 *  @memberof Utilities */
function clamp(value, min=0, max=1) { return value < min ? min : value > max ? max : value; }

/** Returns what percentage the value is between valueA and valueB
 *  @param {Number} value
 *  @param {Number} valueA
 *  @param {Number} valueB
 *  @return {Number}
 *  @memberof Utilities */
function percent(value, valueA, valueB)
{ return (valueB-=valueA) ? clamp((value-valueA)/valueB) : 0; }

/** Linearly interpolates between values passed in using percent
 *  @param {Number} percent
 *  @param {Number} valueA
 *  @param {Number} valueB
 *  @return {Number}
 *  @memberof Utilities */
function lerp(percent, valueA, valueB) { return valueA + clamp(percent) * (valueB-valueA); }

/** Returns signed wrapped distance between the two values passed in
 *  @param {Number} valueA
 *  @param {Number} valueB
 *  @param {Number} [wrapSize]
 *  @returns {Number}
 *  @memberof Utilities */
function distanceWrap(valueA, valueB, wrapSize=1)
{ const d = (valueA - valueB) % wrapSize; return d*2 % wrapSize - d; }

/** Linearly interpolates between values passed in with wrapping
 *  @param {Number} percent
 *  @param {Number} valueA
 *  @param {Number} valueB
 *  @param {Number} [wrapSize]
 *  @returns {Number}
 *  @memberof Utilities */
function lerpWrap(percent, valueA, valueB, wrapSize=1)
{ return valueB + clamp(percent) * distanceWrap(valueA, valueB, wrapSize); }

/** Returns signed wrapped distance between the two angles passed in
 *  @param {Number} angleA
 *  @param {Number} angleB
 *  @returns {Number}
 *  @memberof Utilities */
function distanceAngle(angleA, angleB) { return distanceWrap(angleA, angleB, 2*PI); }

/** Linearly interpolates between the angles passed in with wrapping
 *  @param {Number} percent
 *  @param {Number} angleA
 *  @param {Number} angleB
 *  @returns {Number}
 *  @memberof Utilities */
function lerpAngle(percent, angleA, angleB) { return lerpWrap(percent, angleA, angleB, 2*PI); }

/** Applies smoothstep function to the percentage value
 *  @param {Number} percent
 *  @return {Number}
 *  @memberof Utilities */
function smoothStep(percent) { return percent * percent * (3 - 2 * percent); }

/** Returns the nearest power of two not less then the value
 *  @param {Number} value
 *  @return {Number}
 *  @memberof Utilities */
function nearestPowerOfTwo(value) { return 2**Math.ceil(Math.log2(value)); }

/** Returns true if two axis aligned bounding boxes are overlapping 
 *  @param {Vector2} posA          - Center of box A
 *  @param {Vector2} sizeA         - Size of box A
 *  @param {Vector2} posB          - Center of box B
 *  @param {Vector2} [sizeB=(0,0)] - Size of box B, a point if undefined
 *  @return {Boolean}              - True if overlapping
 *  @memberof Utilities */
function isOverlapping(posA, sizeA, posB, sizeB=vec2())
{ 
    return abs(posA.x - posB.x)*2 < sizeA.x + sizeB.x 
        && abs(posA.y - posB.y)*2 < sizeA.y + sizeB.y;
}

/** Returns true if a line segment is intersecting an axis aligned box
 *  @param {Vector2} start - Start of raycast
 *  @param {Vector2} end   - End of raycast
 *  @param {Vector2} pos   - Center of box
 *  @param {Vector2} size  - Size of box
 *  @return {Boolean}      - True if intersecting
 *  @memberof Utilities */
function isIntersecting(start, end, pos, size)
{
    // Liang-Barsky algorithm
    const boxMin = pos.subtract(size.scale(.5));
    const boxMax = boxMin.add(size);
    const delta = end.subtract(start);
    const a = start.subtract(boxMin);
    const b = start.subtract(boxMax);
    const p = [-delta.x, delta.x, -delta.y, delta.y];
    const q = [a.x, -b.x, a.y, -b.y];
    let tMin = 0, tMax = 1;
    for (let i = 4; i--;)
    {
        if (p[i])
        {
            const t = q[i] / p[i];
            if (p[i] < 0)
            {
                if (t > tMax) return false;
                tMin = max(t, tMin);
            }
            else
            {
                if (t < tMin) return false;
                tMax = min(t, tMax);
            }
        }
        else if (q[i] < 0)
            return false;
    }

    return true;
}

/** Returns an oscillating wave between 0 and amplitude with frequency of 1 Hz by default
 *  @param {Number} [frequency] - Frequency of the wave in Hz
 *  @param {Number} [amplitude] - Amplitude (max height) of the wave
 *  @param {Number} [t=time]    - Value to use for time of the wave
 *  @return {Number}            - Value waving between 0 and amplitude
 *  @memberof Utilities */
function wave(frequency=1, amplitude=1, t=time)
{ return amplitude/2 * (1 - Math.cos(t*frequency*2*PI)); }

/** Formats seconds to mm:ss style for display purposes 
 *  @param {Number} t - time in seconds
 *  @return {String}
 *  @memberof Utilities */
function formatTime(t) { return (t/60|0) + ':' + (t%60<10?'0':'') + (t%60|0); }

///////////////////////////////////////////////////////////////////////////////

/** Random global functions
 *  @namespace Random */

/** Returns a random value between the two values passed in
 *  @param {Number} [valueA]
 *  @param {Number} [valueB]
 *  @return {Number}
 *  @memberof Random */
function rand(valueA=1, valueB=0) { return valueB + Math.random() * (valueA-valueB); }

/** Returns a floored random value the two values passed in
 *  @param {Number} valueA
 *  @param {Number} [valueB]
 *  @return {Number}
 *  @memberof Random */
function randInt(valueA, valueB=0) { return Math.floor(rand(valueA,valueB)); }

/** Randomly returns either -1 or 1
 *  @return {Number}
 *  @memberof Random */
function randSign() { return randInt(2) * 2 - 1; }

/** Returns a random Vector2 with the passed in length
 *  @param {Number} [length]
 *  @return {Vector2}
 *  @memberof Random */
function randVector(length=1) { return new Vector2().setAngle(rand(2*PI), length); }

/** Returns a random Vector2 within a circular shape
 *  @param {Number} [radius]
 *  @param {Number} [minRadius]
 *  @return {Vector2}
 *  @memberof Random */
function randInCircle(radius=1, minRadius=0)
{ return radius > 0 ? randVector(radius * rand(minRadius / radius, 1)**.5) : new Vector2; }

/** Returns a random color between the two passed in colors, combine components if linear
 *  @param {Color}   [colorA=(1,1,1,1)]
 *  @param {Color}   [colorB=(0,0,0,1)]
 *  @param {Boolean} [linear]
 *  @return {Color}
 *  @memberof Random */
function randColor(colorA=new Color, colorB=new Color(0,0,0,1), linear=false)
{
    return linear ? colorA.lerp(colorB, rand()) : 
        new Color(rand(colorA.r,colorB.r), rand(colorA.g,colorB.g), rand(colorA.b,colorB.b), rand(colorA.a,colorB.a));
}

///////////////////////////////////////////////////////////////////////////////

/** 
 * Seeded random number generator
 * - Can be used to create a deterministic random number sequence
 * @example
 * let r = new RandomGenerator(123); // random number generator with seed 123
 * let a = r.float();                // random value between 0 and 1
 * let b = r.int(10);                // random integer between 0 and 9
 * r.seed = 123;                     // reset the seed
 * let c = r.float();                // the same value as a
 */
class RandomGenerator
{
    /** Create a random number generator with the seed passed in
     *  @param {Number} seed - Starting seed */
    constructor(seed)
    {
        /** @property {Number} - random seed */
        this.seed = seed;
    }

    /** Returns a seeded random value between the two values passed in
    *  @param {Number} [valueA]
    *  @param {Number} [valueB]
    *  @return {Number} */
    float(valueA=1, valueB=0)
    {
        // xorshift algorithm
        this.seed ^= this.seed << 13; 
        this.seed ^= this.seed >>> 17; 
        this.seed ^= this.seed << 5;
        return valueB + (valueA - valueB) * abs(this.seed % 1e8) / 1e8;
    }

    /** Returns a floored seeded random value the two values passed in
    *  @param {Number} valueA
    *  @param {Number} [valueB]
    *  @return {Number} */
    int(valueA, valueB=0) { return Math.floor(this.float(valueA, valueB)); }

    /** Randomly returns either -1 or 1 deterministically
    *  @return {Number} */
    sign() { return this.float() > .5 ? 1 : -1; }
}

///////////////////////////////////////////////////////////////////////////////

/** 
 * Create a 2d vector, can take another Vector2 to copy, 2 scalars, or 1 scalar
 * @param {(Number|Vector2)} [x]
 * @param {Number} [y]
 * @return {Vector2}
 * @example
 * let a = vec2(0, 1); // vector with coordinates (0, 1)
 * let b = vec2(a);    // copy a into b
 * a = vec2(5);        // set a to (5, 5)
 * b = vec2();         // set b to (0, 0)
 * @memberof Utilities
 */
function vec2(x=0, y)
{
    return typeof x == 'number' ? 
        new Vector2(x, y == undefined? x : y) : 
        new Vector2(x.x, x.y);
}

/** 
 * Check if object is a valid Vector2
 * @param {any} v
 * @return {Boolean}
 * @memberof Utilities
 */
function isVector2(v) { return v instanceof Vector2; }

/** 
 * 2D Vector object with vector math library
 * - Functions do not change this so they can be chained together
 * @example
 * let a = new Vector2(2, 3); // vector with coordinates (2, 3)
 * let b = new Vector2;       // vector with coordinates (0, 0)
 * let c = vec2(4, 2);        // use the vec2 function to make a Vector2
 * let d = a.add(b).scale(5); // operators can be chained
 */
class Vector2
{
    /** Create a 2D vector with the x and y passed in, can also be created with vec2()
     *  @param {Number} [x] - X axis location
     *  @param {Number} [y] - Y axis location */
    constructor(x=0, y=0)
    {
        ASSERT(typeof x == 'number' && typeof y == 'number');
        /** @property {Number} - X axis location */
        this.x = x;
        /** @property {Number} - Y axis location */
        this.y = y;
    }

    /** Sets values of this vector and returns self
     *  @param {Number} [x] - X axis location
     *  @param {Number} [y] - Y axis location
     *  @return {Vector2} */
    set(x=0, y=0) { this.x=x; this.y=y; return this; }

    /** Returns a new vector that is a copy of this
     *  @return {Vector2} */
    copy() { return new Vector2(this.x, this.y); }

    /** Returns a copy of this vector plus the vector passed in
     *  @param {Vector2} v - other vector
     *  @return {Vector2} */
    add(v)
    {
        ASSERT(isVector2(v));
        return new Vector2(this.x + v.x, this.y + v.y);
    }

    /** Returns a copy of this vector minus the vector passed in
     *  @param {Vector2} v - other vector
     *  @return {Vector2} */
    subtract(v)
    {
        ASSERT(isVector2(v));
        return new Vector2(this.x - v.x, this.y - v.y);
    }

    /** Returns a copy of this vector times the vector passed in
     *  @param {Vector2} v - other vector
     *  @return {Vector2} */
    multiply(v)
    {
        ASSERT(isVector2(v));
        return new Vector2(this.x * v.x, this.y * v.y);
    }

    /** Returns a copy of this vector divided by the vector passed in
     *  @param {Vector2} v - other vector
     *  @return {Vector2} */
    divide(v)
    {
        ASSERT(isVector2(v));
        return new Vector2(this.x / v.x, this.y / v.y);
    }

    /** Returns a copy of this vector scaled by the vector passed in
     *  @param {Number} s - scale
     *  @return {Vector2} */
    scale(s)
    {
        ASSERT(!isVector2(s));
        return new Vector2(this.x * s, this.y * s);
    }

    /** Returns the length of this vector
     * @return {Number} */
    length() { return this.lengthSquared()**.5; }

    /** Returns the length of this vector squared
     * @return {Number} */
    lengthSquared() { return this.x**2 + this.y**2; }

    /** Returns the distance from this vector to vector passed in
     * @param {Vector2} v - other vector
     * @return {Number} */
    distance(v)
    {
        ASSERT(isVector2(v));
        return this.distanceSquared(v)**.5;
    }

    /** Returns the distance squared from this vector to vector passed in
     * @param {Vector2} v - other vector
     * @return {Number} */
    distanceSquared(v)
    {
        ASSERT(isVector2(v));
        return (this.x - v.x)**2 + (this.y - v.y)**2;
    }

    /** Returns a new vector in same direction as this one with the length passed in
     * @param {Number} [length]
     * @return {Vector2} */
    normalize(length=1)
    {
        const l = this.length();
        return l ? this.scale(length/l) : new Vector2(0, length);
    }

    /** Returns a new vector clamped to length passed in
     * @param {Number} [length]
     * @return {Vector2} */
    clampLength(length=1)
    {
        const l = this.length();
        return l > length ? this.scale(length/l) : this;
    }

    /** Returns the dot product of this and the vector passed in
     * @param {Vector2} v - other vector
     * @return {Number} */
    dot(v)
    {
        ASSERT(isVector2(v));
        return this.x*v.x + this.y*v.y;
    }

    /** Returns the cross product of this and the vector passed in
     * @param {Vector2} v - other vector
     * @return {Number} */
    cross(v)
    {
        ASSERT(isVector2(v));
        return this.x*v.y - this.y*v.x;
    }

    /** Returns the angle of this vector, up is angle 0
     * @return {Number} */
    angle() { return Math.atan2(this.x, this.y); }

    /** Sets this vector with angle and length passed in
     * @param {Number} [angle]
     * @param {Number} [length]
     * @return {Vector2} */
    setAngle(angle=0, length=1) 
    {
        this.x = length*Math.sin(angle);
        this.y = length*Math.cos(angle);
        return this;
    }

    /** Returns copy of this vector rotated by the angle passed in
     * @param {Number} angle
     * @return {Vector2} */
    rotate(angle)
    { 
        const c = Math.cos(angle), s = Math.sin(angle); 
        return new Vector2(this.x*c - this.y*s, this.x*s + this.y*c);
    }

    /** Set the integer direction of this vector, corrosponding to multiples of 90 degree rotation (0-3)
     * @param {Number} [direction]
     * @param {Number} [length] */
    setDirection(direction, length=1)
    {
        ASSERT(direction==0 || direction==1 || direction==2 || direction==3);
        return vec2(direction%2 ? direction-1 ? -length : length : 0, 
            direction%2 ? 0 : direction ? -length : length);
    }

    /** Returns the integer direction of this vector, corrosponding to multiples of 90 degree rotation (0-3)
     * @return {Number} */
    direction()
    { return abs(this.x) > abs(this.y) ? this.x < 0 ? 3 : 1 : this.y < 0 ? 2 : 0; }

    /** Returns a copy of this vector that has been inverted
     * @return {Vector2} */
    invert() { return new Vector2(this.y, -this.x); }

    /** Returns a copy of this vector with each axis floored
     * @return {Vector2} */
    floor() { return new Vector2(Math.floor(this.x), Math.floor(this.y)); }

    /** Returns the area this vector covers as a rectangle
     * @return {Number} */
    area() { return abs(this.x * this.y); }

    /** Returns a new vector that is p percent between this and the vector passed in
     * @param {Vector2} v - other vector
     * @param {Number}  percent
     * @return {Vector2} */
    lerp(v, percent)
    {
        ASSERT(isVector2(v));
        return this.add(v.subtract(this).scale(clamp(percent)));
    }

    /** Returns true if this vector is within the bounds of an array size passed in
     * @param {Vector2} arraySize
     * @return {Boolean} */
    arrayCheck(arraySize)
    {
        ASSERT(isVector2(arraySize));
        return this.x >= 0 && this.y >= 0 && this.x < arraySize.x && this.y < arraySize.y;
    }

    /** Returns this vector expressed as a string
     * @param {Number} digits - precision to display
     * @return {String} */
    toString(digits=3) 
    {
        if (debug)
            return `(${(this.x<0?'':' ') + this.x.toFixed(digits)},${(this.y<0?'':' ') + this.y.toFixed(digits)} )`;
    }
}

///////////////////////////////////////////////////////////////////////////////

/** 
 * Create a color object with RGBA values, white by default
 * @param {Number} [r=1] - red
 * @param {Number} [g=1] - green
 * @param {Number} [b=1] - blue
 * @param {Number} [a=1] - alpha
 * @return {Color}
 * @memberof Utilities
 */
function rgb(r, g, b, a) { return new Color(r, g, b, a); }

/** 
 * Create a color object with HSLA values, white by default
 * @param {Number} [h=0] - hue
 * @param {Number} [s=0] - saturation
 * @param {Number} [l=1] - lightness
 * @param {Number} [a=1] - alpha
 * @return {Color}
 * @memberof Utilities
 */
function hsl(h, s, l, a) { return new Color().setHSLA(h, s, l, a); }

/** 
 * Check if object is a valid Color
 * @param {any} c
 * @return {Boolean}
 * @memberof Utilities
 */
function isColor(c) { return c instanceof Color; }

/** 
 * Color object (red, green, blue, alpha) with some helpful functions
 * @example
 * let a = new Color;              // white
 * let b = new Color(1, 0, 0);     // red
 * let c = new Color(0, 0, 0, 0);  // transparent black
 * let d = rgb(0, 0, 1);           // blue using rgb color
 * let e = hsl(.3, 1, .5);         // green using hsl color
 */
class Color
{
    /** Create a color with the rgba components passed in, white by default
     *  @param {Number} [r] - red
     *  @param {Number} [g] - green
     *  @param {Number} [b] - blue
     *  @param {Number} [a] - alpha*/
    constructor(r=1, g=1, b=1, a=1)
    {
        /** @property {Number} - Red */
        this.r = r;
        /** @property {Number} - Green */
        this.g = g;
        /** @property {Number} - Blue */
        this.b = b;
        /** @property {Number} - Alpha */
        this.a = a;
    }

    /** Sets values of this color and returns self
     *  @param {Number} [r] - red
     *  @param {Number} [g] - green
     *  @param {Number} [b] - blue
     *  @param {Number} [a] - alpha
     *  @return {Color} */
    set(r=1, g=1, b=1, a=1)
    { this.r=r; this.g=g; this.b=b; this.a=a; return this; }

    /** Returns a new color that is a copy of this
     * @return {Color} */
    copy() { return new Color(this.r, this.g, this.b, this.a); }

    /** Returns a copy of this color plus the color passed in
     * @param {Color} c - other color
     * @return {Color} */
    add(c)
    {
        ASSERT(isColor(c));
        return new Color(this.r+c.r, this.g+c.g, this.b+c.b, this.a+c.a);
    }

    /** Returns a copy of this color minus the color passed in
     * @param {Color} c - other color
     * @return {Color} */
    subtract(c)
    {
        ASSERT(isColor(c));
        return new Color(this.r-c.r, this.g-c.g, this.b-c.b, this.a-c.a);
    }

    /** Returns a copy of this color times the color passed in
     * @param {Color} c - other color
     * @return {Color} */
    multiply(c)
    {
        ASSERT(isColor(c));
        return new Color(this.r*c.r, this.g*c.g, this.b*c.b, this.a*c.a);
    }

    /** Returns a copy of this color divided by the color passed in
     * @param {Color} c - other color
     * @return {Color} */
    divide(c)
    {
        ASSERT(isColor(c));
        return new Color(this.r/c.r, this.g/c.g, this.b/c.b, this.a/c.a);
    }

    /** Returns a copy of this color scaled by the value passed in, alpha can be scaled separately
     * @param {Number} scale
     * @param {Number} [alphaScale=scale]
     * @return {Color} */
    scale(scale, alphaScale=scale) 
    { return new Color(this.r*scale, this.g*scale, this.b*scale, this.a*alphaScale); }

    /** Returns a copy of this color clamped to the valid range between 0 and 1
     * @return {Color} */
    clamp() { return new Color(clamp(this.r), clamp(this.g), clamp(this.b), clamp(this.a)); }

    /** Returns a new color that is p percent between this and the color passed in
     * @param {Color}  c - other color
     * @param {Number} percent
     * @return {Color} */
    lerp(c, percent)
    {
        ASSERT(isColor(c));
        return this.add(c.subtract(this).scale(clamp(percent)));
    }

    /** Sets this color given a hue, saturation, lightness, and alpha
     * @param {Number} [h] - hue
     * @param {Number} [s] - saturation
     * @param {Number} [l] - lightness
     * @param {Number} [a] - alpha
     * @return {Color} */
    setHSLA(h=0, s=0, l=1, a=1)
    {
        h = mod(h,1);
        s = clamp(s);
        l = clamp(l);
        const q = l < .5 ? l*(1+s) : l+s-l*s, p = 2*l-q,
            f = (p, q, t)=>
                (t = mod(t,1))*6 < 1 ? p+(q-p)*6*t :
                t*2 < 1 ? q :
                t*3 < 2 ? p+(q-p)*(4-t*6) : p;
        this.r = f(p, q, h + 1/3);
        this.g = f(p, q, h);
        this.b = f(p, q, h - 1/3);
        this.a = a;
        return this;
    }

    /** Returns this color expressed in hsla format
     * @return {Array} */
    HSLA()
    {
        const r = clamp(this.r);
        const g = clamp(this.g);
        const b = clamp(this.b);
        const a = clamp(this.a);
        const max = Math.max(r, g, b);
        const min = Math.min(r, g, b);
        const l = (max + min) / 2;
        
        let h = 0, s = 0;
        if (max != min)
        {
            let d = max - min;
            s = l > .5 ? d / (2 - max - min) : d / (max + min);
            if (r == max)
                h = (g - b) / d + (g < b ? 6 : 0);
            else if (g == max)
                h = (b - r) / d + 2;
            else if (b == max)
                h =  (r - g) / d + 4;
        }

        return [h / 6, s, l, a];
    }

    /** Returns a new color that has each component randomly adjusted
     * @param {Number} [amount]
     * @param {Number} [alphaAmount]
     * @return {Color} */
    mutate(amount=.05, alphaAmount=0) 
    {
        return new Color
        (
            this.r + rand(amount, -amount),
            this.g + rand(amount, -amount),
            this.b + rand(amount, -amount),
            this.a + rand(alphaAmount, -alphaAmount)
        ).clamp();
    }

    /** Returns this color expressed as a hex color code
     * @param {Boolean} [useAlpha] - if alpha should be included in result
     * @return {String} */
    toString(useAlpha = true)      
    { 
        const toHex = (c)=> ((c=c*255|0)<16 ? '0' : '') + c.toString(16);
        return '#' + toHex(this.r) + toHex(this.g) + toHex(this.b) + (useAlpha ? toHex(this.a) : '');
    }
    
    /** Set this color from a hex code
     * @param {String} hex - html hex code
     * @return {Color} */
    setHex(hex)
    {
        const fromHex = (c)=> clamp(parseInt(hex.slice(c,c+2),16)/255);
        this.r = fromHex(1);
        this.g = fromHex(3),
        this.b = fromHex(5);
        this.a = hex.length > 7 ? fromHex(7) : 1;
        return this;
    }
    
    /** Returns this color expressed as 32 bit RGBA value
     * @return {Number} */
    rgbaInt()  
    {
        const r = clamp(this.r)*255|0;
        const g = clamp(this.g)*255<<8;
        const b = clamp(this.b)*255<<16;
        const a = clamp(this.a)*255<<24;
        return r + g + b + a;
    }
}

///////////////////////////////////////////////////////////////////////////////
// default colors

/** Color - White
 *  @type {Color}
 *  @memberof Utilities */
const WHITE = rgb();

/** Color - Black
 *  @type {Color}
 *  @memberof Utilities */
const BLACK = rgb(0,0,0);

/** Color - Gray
 *  @type {Color}
 *  @memberof Utilities */
const GRAY = rgb(.5,.5,.5);

/** Color - Red
 *  @type {Color}
 *  @memberof Utilities */
const RED = rgb(1,0,0);

/** Color - Orange
 *  @type {Color}
 *  @memberof Utilities */
const ORANGE = rgb(1,.5,0);

/** Color - Yellow
 *  @type {Color}
 *  @memberof Utilities */
const YELLOW = rgb(1,1,0);

/** Color - Green
 *  @type {Color}
 *  @memberof Utilities */
const GREEN = rgb(0,1,0);

/** Color - Cyan
 *  @type {Color}
 *  @memberof Utilities */
const CYAN = rgb(0,1,1);

/** Color - Blue
 *  @type {Color}
 *  @memberof Utilities */
const BLUE = rgb(0,0,1);

/** Color - Purple
 *  @type {Color}
 *  @memberof Utilities */
const PURPLE = rgb(.5,0,1);

/** Color - Magenta
 *  @type {Color}
 *  @memberof Utilities */
const MAGENTA = rgb(1,0,1);

///////////////////////////////////////////////////////////////////////////////

/**
 * Timer object tracks how long has passed since it was set
 * @example
 * let a = new Timer;    // creates a timer that is not set
 * a.set(3);             // sets the timer to 3 seconds
 *
 * let b = new Timer(1); // creates a timer with 1 second left
 * b.unset();            // unsets the timer
 */
class Timer
{
    /** Create a timer object set time passed in
     *  @param {Number} [timeLeft] - How much time left before the timer elapses in seconds */
    constructor(timeLeft) { this.time = timeLeft == undefined ? undefined : time + timeLeft; this.setTime = timeLeft; }

    /** Set the timer with seconds passed in
     *  @param {Number} [timeLeft] - How much time left before the timer is elapsed in seconds */
    set(timeLeft=0) { this.time = time + timeLeft; this.setTime = timeLeft; }

    /** Unset the timer */
    unset() { this.time = undefined; }

    /** Returns true if set
     * @return {Boolean} */
    isSet() { return this.time != undefined; }

    /** Returns true if set and has not elapsed
     * @return {Boolean} */
    active() { return time < this.time; }

    /** Returns true if set and elapsed
     * @return {Boolean} */
    elapsed() { return time >= this.time; }

    /** Get how long since elapsed, returns 0 if not set (returns negative if currently active)
     * @return {Number} */
    get() { return this.isSet()? time - this.time : 0; }

    /** Get percentage elapsed based on time it was set to, returns 0 if not set
     * @return {Number} */
    getPercent() { return this.isSet()? percent(this.time - time, this.setTime, 0) : 0; }
    
    /** Returns this timer expressed as a string
     * @return {String} */
    toString() { if (debug) { return this.isSet() ? Math.abs(this.get()) + ' seconds ' + (this.get()<0 ? 'before' : 'after' ) : 'unset'; }}
    
    /** Get how long since elapsed, returns 0 if not set (returns negative if currently active)
     * @return {Number} */
    valueOf()               { return this.get(); }
}
/**
 * LittleJS Engine Settings
 * - All settings for the engine are here
 * @namespace Settings
 */



///////////////////////////////////////////////////////////////////////////////
// Camera settings

/** Position of camera in world space
 *  @type {Vector2}
 *  @default Vector2()
 *  @memberof Settings */
let cameraPos = vec2();

/** Scale of camera in world space
 *  @type {Number}
 *  @default
 *  @memberof Settings */
let cameraScale = 32;

///////////////////////////////////////////////////////////////////////////////
// Display settings

/** The max size of the canvas, centered if window is larger
 *  @type {Vector2}
 *  @default Vector2(1920,1080)
 *  @memberof Settings */
let canvasMaxSize = vec2(1920, 1080);

/** Fixed size of the canvas, if enabled canvas size never changes
 * - you may also need to set mainCanvasSize if using screen space coords in startup
 *  @type {Vector2}
 *  @default Vector2()
 *  @memberof Settings */
let canvasFixedSize = vec2();

/** Disables filtering for crisper pixel art if true
 *  @type {Boolean}
 *  @default
 *  @memberof Settings */
let canvasPixelated = true;

/** Default font used for text rendering
 *  @type {String}
 *  @default
 *  @memberof Settings */
let fontDefault = 'arial';

/** Enable to show the LittleJS splash screen be shown on startup
 *  @type {Boolean}
 *  @default
 *  @memberof Settings */
let showSplashScreen = false;

/** Disables all rendering, audio, and input for servers
 *  @type {Boolean}
 *  @default
 *  @memberof Settings */
let headlessMode = false;

///////////////////////////////////////////////////////////////////////////////
// WebGL settings

/** Enable webgl rendering, webgl can be disabled and removed from build (with some features disabled)
 *  @type {Boolean}
 *  @default
 *  @memberof Settings */
let glEnable = true;

/** Fixes slow rendering in some browsers by not compositing the WebGL canvas
 *  @type {Boolean}
 *  @default
 *  @memberof Settings */
let glOverlay = true;

///////////////////////////////////////////////////////////////////////////////
// Tile sheet settings

/** Default size of tiles in pixels
 *  @type {Vector2}
 *  @default Vector2(16,16)
 *  @memberof Settings */
let tileSizeDefault = vec2(16);

/** How many pixels smaller to draw tiles to prevent bleeding from neighbors
 *  @type {Number}
 *  @default
 *  @memberof Settings */
let tileFixBleedScale = .5;

///////////////////////////////////////////////////////////////////////////////
// Object settings

/** Enable physics solver for collisions between objects
 *  @type {Boolean}
 *  @default
 *  @memberof Settings */
let enablePhysicsSolver = true;

/** Default object mass for collision calcuations (how heavy objects are)
 *  @type {Number}
 *  @default
 *  @memberof Settings */
let objectDefaultMass = 1;

/** How much to slow velocity by each frame (0-1)
 *  @type {Number}
 *  @default
 *  @memberof Settings */
let objectDefaultDamping = 1;

/** How much to slow angular velocity each frame (0-1)
 *  @type {Number}
 *  @default
 *  @memberof Settings */
let objectDefaultAngleDamping = 1;

/** How much to bounce when a collision occurs (0-1)
 *  @type {Number}
 *  @default
 *  @memberof Settings */
let objectDefaultElasticity = 0;

/** How much to slow when touching (0-1)
 *  @type {Number}
 *  @default
 *  @memberof Settings */
let objectDefaultFriction = .8;

/** Clamp max speed to avoid fast objects missing collisions
 *  @type {Number}
 *  @default
 *  @memberof Settings */
let objectMaxSpeed = 1;

/** How much gravity to apply to objects along the Y axis, negative is down
 *  @type {Number}
 *  @default
 *  @memberof Settings */
let gravity = 0;

/** Scales emit rate of particles, useful for low graphics mode (0 disables particle emitters)
 *  @type {Number}
 *  @default
 *  @memberof Settings */
let particleEmitRateScale = 1;

///////////////////////////////////////////////////////////////////////////////
// Input settings

/** Should gamepads be allowed
 *  @type {Boolean}
 *  @default
 *  @memberof Settings */
let gamepadsEnable = true;

/** If true, the dpad input is also routed to the left analog stick (for better accessability)
 *  @type {Boolean}
 *  @default
 *  @memberof Settings */
let gamepadDirectionEmulateStick = true;

/** If true the WASD keys are also routed to the direction keys (for better accessability)
 *  @type {Boolean}
 *  @default
 *  @memberof Settings */
let inputWASDEmulateDirection = true;

/** True if touch input is enabled for mobile devices
 *  - Touch events will be routed to mouse events
 *  @type {Boolean}
 *  @default
 *  @memberof Settings */
let touchInputEnable = true;

/** True if touch gamepad should appear on mobile devices
 *  - Supports left analog stick, 4 face buttons and start button (button 9)
 *  - Must be set by end of gameInit to be activated
 *  @type {Boolean}
 *  @default
 *  @memberof Settings */
let touchGamepadEnable = false;

/** True if touch gamepad should be analog stick or false to use if 8 way dpad
 *  @type {Boolean}
 *  @default
 *  @memberof Settings */
let touchGamepadAnalog = true;

/** Size of virtual gamepad for touch devices in pixels
 *  @type {Number}
 *  @default
 *  @memberof Settings */
let touchGamepadSize = 99;

/** Transparency of touch gamepad overlay
 *  @type {Number}
 *  @default
 *  @memberof Settings */
let touchGamepadAlpha = .3;

/** Allow vibration hardware if it exists
 *  @type {Boolean}
 *  @default
 *  @memberof Settings */
let vibrateEnable = true;

///////////////////////////////////////////////////////////////////////////////
// Audio settings

/** All audio code can be disabled and removed from build
 *  @type {Boolean}
 *  @default
 *  @memberof Settings */
let soundEnable = true;

/** Volume scale to apply to all sound, music and speech
 *  @type {Number}
 *  @default
 *  @memberof Settings */
let soundVolume = .3;

/** Default range where sound no longer plays
 *  @type {Number}
 *  @default
 *  @memberof Settings */
let soundDefaultRange = 40;

/** Default range percent to start tapering off sound (0-1)
 *  @type {Number}
 *  @default
 *  @memberof Settings */
let soundDefaultTaper = .7;

///////////////////////////////////////////////////////////////////////////////
// Medals settings

/** How long to show medals for in seconds
 *  @type {Number}
 *  @default
 *  @memberof Settings */
let medalDisplayTime = 5;

/** How quickly to slide on/off medals in seconds
 *  @type {Number}
 *  @default
 *  @memberof Settings */
let medalDisplaySlideTime = .5;

/** Size of medal display
 *  @type {Vector2}
 *  @default Vector2(640,80)
 *  @memberof Settings */
let medalDisplaySize = vec2(640, 80);

/** Size of icon in medal display
 *  @type {Number}
 *  @default
 *  @memberof Settings */
let medalDisplayIconSize = 50;

/** Set to stop medals from being unlockable (like if cheats are enabled)
 *  @type {Boolean}
 *  @default
 *  @memberof Settings */
let medalsPreventUnlock = false;

///////////////////////////////////////////////////////////////////////////////
// Setters for global variables

/** Set position of camera in world space
 *  @param {Vector2} pos
 *  @memberof Settings */
function setCameraPos(pos) { cameraPos = pos; }

/** Set scale of camera in world space
 *  @param {Number} scale
 *  @memberof Settings */
function setCameraScale(scale) { cameraScale = scale; }

/** Set max size of the canvas
 *  @param {Vector2} size
 *  @memberof Settings */
function setCanvasMaxSize(size) { canvasMaxSize = size; }

/** Set fixed size of the canvas
 *  @param {Vector2} size
 *  @memberof Settings */
function setCanvasFixedSize(size) { canvasFixedSize = size; }

/** Disables anti aliasing for pixel art if true
 *  @param {Boolean} pixelated
 *  @memberof Settings */
function setCanvasPixelated(pixelated) { canvasPixelated = pixelated; }

/** Set default font used for text rendering
 *  @param {String} font
 *  @memberof Settings */
function setFontDefault(font) { fontDefault = font; }

/** Set if the LittleJS splash screen be shown on startup
 *  @param {Boolean} show
 *  @memberof Settings */
function setShowSplashScreen(show) { showSplashScreen = show; }

/** Set to disalbe rendering, audio, and input for servers
 *  @param {Boolean} headless
 *  @memberof Settings */
function setHeadlessMode(headless) { headlessMode = headless; }

/** Set if webgl rendering is enabled
 *  @param {Boolean} enable
 *  @memberof Settings */
function setGlEnable(enable) { glEnable = enable; }

/** Set to not composite the WebGL canvas
 *  @param {Boolean} overlay
 *  @memberof Settings */
function setGlOverlay(overlay) { glOverlay = overlay; }

/** Set default size of tiles in pixels
 *  @param {Vector2} size
 *  @memberof Settings */
function setTileSizeDefault(size) { tileSizeDefault = size; }

/** Set to prevent tile bleeding from neighbors in pixels
 *  @param {Number} scale
 *  @memberof Settings */
function setTileFixBleedScale(scale) { tileFixBleedScale = scale; }

/** Set if collisions between objects are enabled
 *  @param {Boolean} enable
 *  @memberof Settings */
function setEnablePhysicsSolver(enable) { enablePhysicsSolver = enable; }

/** Set default object mass for collison calcuations
 *  @param {Number} mass
 *  @memberof Settings */
function setObjectDefaultMass(mass) { objectDefaultMass = mass; }

/** Set how much to slow velocity by each frame
 *  @param {Number} damp
 *  @memberof Settings */
function setObjectDefaultDamping(damp) { objectDefaultDamping = damp; }

/** Set how much to slow angular velocity each frame
 *  @param {Number} damp
 *  @memberof Settings */
function setObjectDefaultAngleDamping(damp) { objectDefaultAngleDamping = damp; }

/** Set how much to bounce when a collision occur
 *  @param {Number} elasticity
 *  @memberof Settings */
function setObjectDefaultElasticity(elasticity) { objectDefaultElasticity = elasticity; }

/** Set how much to slow when touching
 *  @param {Number} friction
 *  @memberof Settings */
function setObjectDefaultFriction(friction) { objectDefaultFriction = friction; }

/** Set max speed to avoid fast objects missing collisions
 *  @param {Number} speed
 *  @memberof Settings */
function setObjectMaxSpeed(speed) { objectMaxSpeed = speed; }

/** Set how much gravity to apply to objects along the Y axis
 *  @param {Number} newGravity
 *  @memberof Settings */
function setGravity(newGravity) { gravity = newGravity; }

/** Set to scales emit rate of particles
 *  @param {Number} scale
 *  @memberof Settings */
function setParticleEmitRateScale(scale) { particleEmitRateScale = scale; }

/** Set if gamepads are enabled
 *  @param {Boolean} enable
 *  @memberof Settings */
function setGamepadsEnable(enable) { gamepadsEnable = enable; }

/** Set if the dpad input is also routed to the left analog stick
 *  @param {Boolean} enable
 *  @memberof Settings */
function setGamepadDirectionEmulateStick(enable) { gamepadDirectionEmulateStick = enable; }

/** Set if true the WASD keys are also routed to the direction keys
 *  @param {Boolean} enable
 *  @memberof Settings */
function setInputWASDEmulateDirection(enable) { inputWASDEmulateDirection = enable; }

/** Set if touch input is allowed
 *  @param {Boolean} enable
 *  @memberof Settings */
function setTouchInputEnable(enable) { touchInputEnable = enable; }

/** Set if touch gamepad should appear on mobile devices
 *  @param {Boolean} enable
 *  @memberof Settings */
function setTouchGamepadEnable(enable) { touchGamepadEnable = enable; }

/** Set if touch gamepad should be analog stick or 8 way dpad
 *  @param {Boolean} analog
 *  @memberof Settings */
function setTouchGamepadAnalog(analog) { touchGamepadAnalog = analog; }

/** Set size of virutal gamepad for touch devices in pixels
 *  @param {Number} size
 *  @memberof Settings */
function setTouchGamepadSize(size) { touchGamepadSize = size; }

/** Set transparency of touch gamepad overlay
 *  @param {Number} alpha
 *  @memberof Settings */
function setTouchGamepadAlpha(alpha) { touchGamepadAlpha = alpha; }

/** Set to allow vibration hardware if it exists
 *  @param {Boolean} enable
 *  @memberof Settings */
function setVibrateEnable(enable) { vibrateEnable = enable; }

/** Set to disable all audio code
 *  @param {Boolean} enable
 *  @memberof Settings */
function setSoundEnable(enable) { soundEnable = enable; }

/** Set volume scale to apply to all sound, music and speech
 *  @param {Number} volume
 *  @memberof Settings */
function setSoundVolume(volume)
{
    soundVolume = volume;
    if (soundEnable && !headlessMode && audioGainNode)
        audioGainNode.gain.value = volume; // update gain immediatly
}

/** Set default range where sound no longer plays
 *  @param {Number} range
 *  @memberof Settings */
function setSoundDefaultRange(range) { soundDefaultRange = range; }

/** Set default range percent to start tapering off sound
 *  @param {Number} taper
 *  @memberof Settings */
function setSoundDefaultTaper(taper) { soundDefaultTaper = taper; }

/** Set how long to show medals for in seconds
 *  @param {Number} time
 *  @memberof Settings */
function setMedalDisplayTime(time) { medalDisplayTime = time; }

/** Set how quickly to slide on/off medals in seconds
 *  @param {Number} time
 *  @memberof Settings */
function setMedalDisplaySlideTime(time) { medalDisplaySlideTime = time; }

/** Set size of medal display
 *  @param {Vector2} size
 *  @memberof Settings */
function setMedalDisplaySize(size) { medalDisplaySize = size; }

/** Set size of icon in medal display
 *  @param {Number} size
 *  @memberof Settings */
function setMedalDisplayIconSize(size) { medalDisplayIconSize = size; }

/** Set to stop medals from being unlockable
 *  @param {Boolean} preventUnlock
 *  @memberof Settings */
function setMedalsPreventUnlock(preventUnlock) { medalsPreventUnlock = preventUnlock; }

/** Set if watermark with FPS should be shown
 *  @param {Boolean} show
 *  @memberof Debug */
function setShowWatermark(show) { showWatermark = show; }

/** Set key code used to toggle debug mode, Esc by default
 *  @param {String} key
 *  @memberof Debug */
function setDebugKey(key) { debugKey = key; }
/** 
 * LittleJS Object System
 */



/** 
 * LittleJS Object Base Object Class
 * - Top level object class used by the engine
 * - Automatically adds self to object list
 * - Will be updated and rendered each frame
 * - Renders as a sprite from a tilesheet by default
 * - Can have color and additive color applied
 * - 2D Physics and collision system
 * - Sorted by renderOrder
 * - Objects can have children attached
 * - Parents are updated before children, and set child transform
 * - Call destroy() to get rid of objects
 *
 * The physics system used by objects is simple and fast with some caveats...
 * - Collision uses the axis aligned size, the object's rotation angle is only for rendering
 * - Objects are guaranteed to not intersect tile collision from physics
 * - If an object starts or is moved inside tile collision, it will not collide with that tile
 * - Collision for objects can be set to be solid to block other objects
 * - Objects may get pushed into overlapping other solid objects, if so they will push away
 * - Solid objects are more performance intensive and should be used sparingly
 * @example
 * // create an engine object, normally you would first extend the class with your own
 * const pos = vec2(2,3);
 * const object = new EngineObject(pos); 
 */
class EngineObject
{
    /** Create an engine object and adds it to the list of objects
     *  @param {Vector2}  [pos=(0,0)]       - World space position of the object
     *  @param {Vector2}  [size=(1,1)]      - World space size of the object
     *  @param {TileInfo} [tileInfo]        - Tile info to render object (undefined is untextured)
     *  @param {Number}   [angle]           - Angle the object is rotated by
     *  @param {Color}    [color=(1,1,1,1)] - Color to apply to tile when rendered
     *  @param {Number}   [renderOrder]     - Objects sorted by renderOrder before being rendered
     */
    constructor(pos=vec2(), size=vec2(1), tileInfo, angle=0, color, renderOrder=0)
    {
        // set passed in params
        ASSERT(isVector2(pos) && isVector2(size), 'ensure pos and size are vec2s');
        ASSERT(typeof tileInfo !== 'number' || !tileInfo, 'old style tile setup');

        /** @property {Vector2} - World space position of the object */
        this.pos = pos.copy();
        /** @property {Vector2} - World space width and height of the object */
        this.size = size;
        /** @property {Vector2} - Size of object used for drawing, uses size if not set */
        this.drawSize = undefined;
        /** @property {TileInfo} - Tile info to render object (undefined is untextured) */
        this.tileInfo = tileInfo;
        /** @property {Number}  - Angle to rotate the object */
        this.angle = angle;
        /** @property {Color}   - Color to apply when rendered */
        this.color = color;
        /** @property {Color}   - Additive color to apply when rendered */
        this.additiveColor = undefined;
        /** @property {Boolean} - Should it flip along y axis when rendered */
        this.mirror = false;

        // physical properties
        /** @property {Number} [mass=objectDefaultMass]                 - How heavy the object is, static if 0 */
        this.mass         = objectDefaultMass;
        /** @property {Number} [damping=objectDefaultDamping]           - How much to slow down velocity each frame (0-1) */
        this.damping      = objectDefaultDamping;
        /** @property {Number} [angleDamping=objectDefaultAngleDamping] - How much to slow down rotation each frame (0-1) */
        this.angleDamping = objectDefaultAngleDamping;
        /** @property {Number} [elasticity=objectDefaultElasticity]     - How bouncy the object is when colliding (0-1) */
        this.elasticity   = objectDefaultElasticity;
        /** @property {Number} [friction=objectDefaultFriction]         - How much friction to apply when sliding (0-1) */
        this.friction     = objectDefaultFriction;
        /** @property {Number}  - How much to scale gravity by for this object */
        this.gravityScale = 1;
        /** @property {Number}  - Objects are sorted by render order */
        this.renderOrder = renderOrder;
        /** @property {Vector2} - Velocity of the object */
        this.velocity = vec2();
        /** @property {Number}  - Angular velocity of the object */
        this.angleVelocity = 0;
        /** @property {Number}  - Track when object was created  */
        this.spawnTime = time;
        /** @property {Array}   - List of children of this object */
        this.children = [];
        /** @property {Boolean}  - Limit object speed using linear or circular math */
        this.clampSpeedLinear = true;

        // parent child system
        /** @property {EngineObject} - Parent of object if in local space  */
        this.parent = undefined;
        /** @property {Vector2}      - Local position if child */
        this.localPos = vec2();
        /** @property {Number}       - Local angle if child  */
        this.localAngle = 0;

        // collision flags
        /** @property {Boolean} - Object collides with the tile collision */
        this.collideTiles = false;
        /** @property {Boolean} - Object collides with solid objects */
        this.collideSolidObjects = false;
        /** @property {Boolean} - Object collides with and blocks other objects */
        this.isSolid = false;
        /** @property {Boolean} - Object collides with raycasts */
        this.collideRaycast = false;

        // add to list of objects
        engineObjects.push(this);
    }
    
    /** Update the object transform, called automatically by engine even when paused */
    updateTransforms()
    {
        const parent = this.parent;
        if (parent)
        {
            // copy parent pos/angle
            const mirror = parent.getMirrorSign();
            this.pos = this.localPos.multiply(vec2(mirror,1)).rotate(-parent.angle).add(parent.pos);
            this.angle = mirror*this.localAngle + parent.angle;
        }

        // update children
        for (const child of this.children)
            child.updateTransforms();
    }

    /** Update the object physics, called automatically by engine once each frame */
    update()
    {
        // child objects do not have physics
        if (this.parent)
            return;

        // limit max speed to prevent missing collisions
        if (this.clampSpeedLinear)
        {
            this.velocity.x = clamp(this.velocity.x, -objectMaxSpeed, objectMaxSpeed);
            this.velocity.y = clamp(this.velocity.y, -objectMaxSpeed, objectMaxSpeed);
        }
        else
        {
            const length2 = this.velocity.lengthSquared();
            if (length2 > objectMaxSpeed*objectMaxSpeed)
            {
                const s = objectMaxSpeed / length2**.5;
                this.velocity.x *= s;
                this.velocity.y *= s;
            }
        }

        // apply physics
        const oldPos = this.pos.copy();
        this.pos.x += this.velocity.x *= this.damping;
        this.pos.y += this.velocity.y = this.damping * this.velocity.y 
            + gravity * this.gravityScale;
        this.angle += this.angleVelocity *= this.angleDamping;

        // physics sanity checks
        ASSERT(this.angleDamping >= 0 && this.angleDamping <= 1);
        ASSERT(this.damping >= 0 && this.damping <= 1);
        if (!enablePhysicsSolver || !this.mass) // dont do collision for fixed objects
            return;

        const wasMovingDown = this.velocity.y < 0;
        if (this.groundObject)
        {
            // apply friction in local space of ground object
            const groundSpeed = this.groundObject.velocity ? this.groundObject.velocity.x : 0;
            this.velocity.x = groundSpeed + (this.velocity.x - groundSpeed) * this.friction;
            this.groundObject = 0;
            //debugOverlay && debugPhysics && debugPoint(this.pos.subtract(vec2(0,this.size.y/2)), '#0f0');
        }

        if (this.collideSolidObjects)
        {
            // check collisions against solid objects
            const epsilon = .001; // necessary to push slightly outside of the collision
            for (const o of engineObjectsCollide)
            {
                // non solid objects don't collide with eachother
                if (!this.isSolid && !o.isSolid || o.destroyed || o.parent || o == this)
                    continue;

                // check collision
                if (!isOverlapping(this.pos, this.size, o.pos, o.size))
                    continue;

                // notify objects of collision and check if should be resolved
                const collide1 = this.collideWithObject(o);
                const collide2 = o.collideWithObject(this);
                if (!collide1 || !collide2)
                    continue;

                if (isOverlapping(oldPos, this.size, o.pos, o.size))
                {
                    // if already was touching, try to push away
                    const deltaPos = oldPos.subtract(o.pos);
                    const length = deltaPos.length();
                    const pushAwayAccel = .001; // push away if already overlapping
                    const velocity = length < .01 ? randVector(pushAwayAccel) : deltaPos.scale(pushAwayAccel/length);
                    this.velocity = this.velocity.add(velocity);
                    if (o.mass) // push away if not fixed
                        o.velocity = o.velocity.subtract(velocity);
                        
                    debugOverlay && debugPhysics && debugOverlap(this.pos, this.size, o.pos, o.size, '#f00');
                    continue;
                }

                // check for collision
                const sizeBoth = this.size.add(o.size);
                const smallStepUp = (oldPos.y - o.pos.y)*2 > sizeBoth.y + gravity; // prefer to push up if small delta
                const isBlockedX = abs(oldPos.y - o.pos.y)*2 < sizeBoth.y;
                const isBlockedY = abs(oldPos.x - o.pos.x)*2 < sizeBoth.x;
                const elasticity = max(this.elasticity, o.elasticity);
                
                if (smallStepUp || isBlockedY || !isBlockedX) // resolve y collision
                {
                    // push outside object collision
                    this.pos.y = o.pos.y + (sizeBoth.y/2 + epsilon) * sign(oldPos.y - o.pos.y);
                    if (o.groundObject && wasMovingDown || !o.mass)
                    {
                        // set ground object if landed on something
                        if (wasMovingDown)
                            this.groundObject = o;

                        // bounce if other object is fixed or grounded
                        this.velocity.y *= -elasticity;
                    }
                    else if (o.mass)
                    {
                        // inelastic collision
                        const inelastic = (this.mass * this.velocity.y + o.mass * o.velocity.y) / (this.mass + o.mass);

                        // elastic collision
                        const elastic0 = this.velocity.y * (this.mass - o.mass) / (this.mass + o.mass)
                            + o.velocity.y * 2 * o.mass / (this.mass + o.mass);
                        const elastic1 = o.velocity.y * (o.mass - this.mass) / (this.mass + o.mass)
                            + this.velocity.y * 2 * this.mass / (this.mass + o.mass);

                        // lerp betwen elastic or inelastic based on elasticity
                        this.velocity.y = lerp(elasticity, inelastic, elastic0);
                        o.velocity.y = lerp(elasticity, inelastic, elastic1);
                    }
                }
                if (!smallStepUp && isBlockedX) // resolve x collision
                {
                    // push outside collision
                    this.pos.x = o.pos.x + (sizeBoth.x/2 + epsilon) * sign(oldPos.x - o.pos.x);
                    if (o.mass)
                    {
                        // inelastic collision
                        const inelastic = (this.mass * this.velocity.x + o.mass * o.velocity.x) / (this.mass + o.mass);

                        // elastic collision
                        const elastic0 = this.velocity.x * (this.mass - o.mass) / (this.mass + o.mass)
                            + o.velocity.x * 2 * o.mass / (this.mass + o.mass);
                        const elastic1 = o.velocity.x * (o.mass - this.mass) / (this.mass + o.mass)
                            + this.velocity.x * 2 * this.mass / (this.mass + o.mass);

                        // lerp betwen elastic or inelastic based on elasticity
                        this.velocity.x = lerp(elasticity, inelastic, elastic0);
                        o.velocity.x = lerp(elasticity, inelastic, elastic1);
                    }
                    else // bounce if other object is fixed
                        this.velocity.x *= -elasticity;
                }
                debugOverlay && debugPhysics && debugOverlap(this.pos, this.size, o.pos, o.size, '#f0f');
            }
        }
        if (this.collideTiles)
        {
            // check collision against tiles
            if (tileCollisionTest(this.pos, this.size, this))
            {
                // if already was stuck in collision, don't do anything
                // this should not happen unless something starts in collision
                if (!tileCollisionTest(oldPos, this.size, this))
                {
                    // test which side we bounced off (or both if a corner)
                    const isBlockedY = tileCollisionTest(vec2(oldPos.x, this.pos.y), this.size, this);
                    const isBlockedX = tileCollisionTest(vec2(this.pos.x, oldPos.y), this.size, this);
                    if (isBlockedY || !isBlockedX)
                    {
                        // bounce velocity
                        this.velocity.y *= -this.elasticity;

                        // set if landed on ground
                        if (this.groundObject = wasMovingDown)
                        {
                            // adjust position to slightly above nearest tile boundary
                            // this prevents gap between object and ground
                            const epsilon = .0001;
                            this.pos.y = (oldPos.y-this.size.y/2|0)+this.size.y/2+epsilon;
                        }
                        else
                        {
                            // move to previous position
                            this.pos.y = oldPos.y;
                        }
                    }
                    if (isBlockedX)
                    {
                        // move to previous position and bounce
                        this.pos.x = oldPos.x;
                        this.velocity.x *= -this.elasticity;
                    }
                }
            }
        }
    }
       
    /** Render the object, draws a tile by default, automatically called each frame, sorted by renderOrder */
    render()
    {
        // default object render
        drawTile(this.pos, this.drawSize || this.size, this.tileInfo, this.color, this.angle, this.mirror, this.additiveColor);
    }
    
    /** Destroy this object, destroy it's children, detach it's parent, and mark it for removal */
    destroy()
    { 
        if (this.destroyed)
            return;
        
        // disconnect from parent and destroy chidren
        this.destroyed = 1;
        this.parent && this.parent.removeChild(this);
        for (const child of this.children)
            child.destroy(child.parent = 0);
    }

    /** Convert from local space to world space
     *  @param {Vector2} pos - local space point */
    localToWorld(pos) { return this.pos.add(pos.rotate(-this.angle)); }

    /** Convert from world space to local space
     *  @param {Vector2} pos - world space point */
    worldToLocal(pos) { return pos.subtract(this.pos).rotate(this.angle); }

    /** Convert from local space to world space for a vector (rotation only)
     *  @param {Vector2} vec - local space vector */
    localToWorldVector(vec) { return vec.rotate(this.angle); }

    /** Convert from world space to local space for a vector (rotation only)
     *  @param {Vector2} vec - world space vector */
    worldToLocalVector(vec) { return vec.rotate(-this.angle); }
    
    /** Called to check if a tile collision should be resolved
     *  @param {Number}  tileData - the value of the tile at the position
     *  @param {Vector2} pos      - tile where the collision occured
     *  @return {Boolean}         - true if the collision should be resolved */
    collideWithTile(tileData, pos)    { return tileData > 0; }

    /** Called to check if a object collision should be resolved
     *  @param {EngineObject} object - the object to test against
     *  @return {Boolean}            - true if the collision should be resolved
     */
    collideWithObject(object)         { return true; }

    /** How long since the object was created
     *  @return {Number} */
    getAliveTime()                    { return time - this.spawnTime; }

    /** Apply acceleration to this object (adjust velocity, not affected by mass)
     *  @param {Vector2} acceleration */
    applyAcceleration(acceleration)   { if (this.mass) this.velocity = this.velocity.add(acceleration); }

    /** Apply force to this object (adjust velocity, affected by mass)
     *  @param {Vector2} force */
    applyForce(force)	              { this.applyAcceleration(force.scale(1/this.mass)); }
    
    /** Get the direction of the mirror
     *  @return {Number} -1 if this.mirror is true, or 1 if not mirrored */
    getMirrorSign() { return this.mirror ? -1 : 1; }

    /** Attaches a child to this with a given local transform
     *  @param {EngineObject} child
     *  @param {Vector2}      [localPos=(0,0)]
     *  @param {Number}       [localAngle] */
    addChild(child, localPos=vec2(), localAngle=0)
    {
        ASSERT(!child.parent && !this.children.includes(child));
        this.children.push(child);
        child.parent = this;
        child.localPos = localPos.copy();
        child.localAngle = localAngle;
    }

    /** Removes a child from this one
     *  @param {EngineObject} child */
    removeChild(child)
    {
        ASSERT(child.parent == this && this.children.includes(child));
        this.children.splice(this.children.indexOf(child), 1);
        child.parent = 0;
    }

    /** Set how this object collides
     *  @param {Boolean} [collideSolidObjects] - Does it collide with solid objects?
     *  @param {Boolean} [isSolid]             - Does it collide with and block other objects? (expensive in large numbers)
     *  @param {Boolean} [collideTiles]        - Does it collide with the tile collision?
     *  @param {Boolean} [collideRaycast]      - Does it collide with raycasts? */
    setCollision(collideSolidObjects=true, isSolid=true, collideTiles=true, collideRaycast=true)
    {
        ASSERT(collideSolidObjects || !isSolid, 'solid objects must be set to collide');

        this.collideSolidObjects = collideSolidObjects;
        this.isSolid = isSolid;
        this.collideTiles = collideTiles;
        this.collideRaycast = collideRaycast;
    }

    /** Returns string containg info about this object for debugging
     *  @return {String} */
    toString()
    {
        if (debug)
        {
            let text = 'type = ' + this.constructor.name;
            if (this.pos.x || this.pos.y)
                text += '\npos = ' + this.pos;
            if (this.velocity.x || this.velocity.y)
                text += '\nvelocity = ' + this.velocity;
            if (this.size.x || this.size.y)
                text += '\nsize = ' + this.size;
            if (this.angle)
                text += '\nangle = ' + this.angle.toFixed(3);
            if (this.color)
                text += '\ncolor = ' + this.color;
            return text;
        }
    }

    /** Render debug info for this object  */
    renderDebugInfo()
    {
        if (debug)
        {
            // show object info for debugging
            const size = vec2(max(this.size.x, .2), max(this.size.y, .2));
            const color1 = rgb(this.collideTiles?1:0, this.collideSolidObjects?1:0, this.isSolid?1:0, this.parent?.2:.5);
            const color2 = this.parent ? rgb(1,1,1,.5) : rgb(0,0,0,.8);
            drawRect(this.pos, size, color1, this.angle, false);
            drawRect(this.pos, size.scale(.8), color2, this.angle, false);
            this.parent && drawLine(this.pos, this.parent.pos, .1, rgb(0,0,1,.5), false);
        }
    }
}
/** 
 * LittleJS Drawing System
 * - Hybrid system with both Canvas2D and WebGL available
 * - Super fast tile sheet rendering with WebGL
 * - Can apply rotation, mirror, color and additive color
 * - Font rendering system with built in engine font
 * - Many useful utility functions
 * 
 * LittleJS uses a hybrid rendering solution with the best of both Canvas2D and WebGL.
 * There are 3 canvas/contexts available to draw to...
 * mainCanvas - 2D background canvas, non WebGL stuff like tile layers are drawn here.
 * glCanvas - Used by the accelerated WebGL batch rendering system.
 * overlayCanvas - Another 2D canvas that appears on top of the other 2 canvases.
 * 
 * The WebGL rendering system is very fast with some caveats...
 * - Switching blend modes (additive) or textures causes another draw call which is expensive in excess
 * - Group additive rendering together using renderOrder to mitigate this issue
 * 
 * The LittleJS rendering solution is intentionally simple, feel free to adjust it for your needs!
 * @namespace Draw
 */



/** The primary 2D canvas visible to the user
 *  @type {HTMLCanvasElement}
 *  @memberof Draw */
let mainCanvas;

/** 2d context for mainCanvas
 *  @type {CanvasRenderingContext2D}
 *  @memberof Draw */
let mainContext;

/** A canvas that appears on top of everything the same size as mainCanvas
 *  @type {HTMLCanvasElement}
 *  @memberof Draw */
let overlayCanvas;

/** 2d context for overlayCanvas
 *  @type {CanvasRenderingContext2D}
 *  @memberof Draw */
let overlayContext;

/** The size of the main canvas (and other secondary canvases) 
 *  @type {Vector2}
 *  @memberof Draw */
let mainCanvasSize = vec2();

/** Array containing texture info for batch rendering system
 *  @type {Array}
 *  @memberof Draw */
let textureInfos = [];

// Keep track of how many draw calls there were each frame for debugging
let drawCount;

///////////////////////////////////////////////////////////////////////////////

/** 
 * Create a tile info object
 * - This can take vecs or floats for easier use and conversion
 * - If an index is passed in, the tile size and index will determine the position
 * @param {(Number|Vector2)} [pos=(0,0)]            - Top left corner of tile in pixels or index
 * @param {(Number|Vector2)} [size=tileSizeDefault] - Size of tile in pixels
 * @param {Number} [textureIndex]                   - Texture index to use
 * @return {TileInfo}
 * @example
 * tile(2)                       // a tile at index 2 using the default tile size of 16
 * tile(5, 8)                    // a tile at index 5 using a tile size of 8
 * tile(1, 16, 3)                // a tile at index 1 of size 16 on texture 3
 * tile(vec2(4,8), vec2(30,10))  // a tile at pixel location (4,8) with a size of (30,10)
 * @memberof Draw
 */
function tile(pos=vec2(), size=tileSizeDefault, textureIndex=0)
{
    if (headlessMode)
        return new TileInfo;

    // if size is a number, make it a vector
    if (typeof size === 'number')
    {
        ASSERT(size > 0);
        size = vec2(size);
    }

    // if pos is a number, use it as a tile index
    if (typeof pos === 'number')
    {
        const textureInfo = textureInfos[textureIndex];
        ASSERT(textureInfo, 'Texture not loaded');
        const cols = textureInfo.size.x / size.x |0;
        pos = vec2((pos%cols)*size.x, (pos/cols|0)*size.y);
    }

    // return a tile info object
    return new TileInfo(pos, size, textureIndex); 
}

/** 
 * Tile Info - Stores info about how to draw a tile
 */
class TileInfo
{
    /** Create a tile info object
     *  @param {Vector2} [pos=(0,0)]            - Top left corner of tile in pixels
     *  @param {Vector2} [size=tileSizeDefault] - Size of tile in pixels
     *  @param {Number}  [textureIndex]         - Texture index to use
     */
    constructor(pos=vec2(), size=tileSizeDefault, textureIndex=0)
    {
        /** @property {Vector2} - Top left corner of tile in pixels */
        this.pos = pos.copy();
        /** @property {Vector2} - Size of tile in pixels */
        this.size = size.copy();
        /** @property {Number} - Texture index to use */
        this.textureIndex = textureIndex;
    }

    /** Returns a copy of this tile offset by a vector
    *  @param {Vector2} offset - Offset to apply in pixels
    *  @return {TileInfo}
    */
    offset(offset)
    { return new TileInfo(this.pos.add(offset), this.size, this.textureIndex); }

    /** Returns a copy of this tile offset by a number of animation frames
    *  @param {Number} frame - Offset to apply in animation frames
    *  @return {TileInfo}
    */
    frame(frame)
    {
        ASSERT(typeof frame == 'number');
        return this.offset(vec2(frame*this.size.x, 0));
    }

    /** Returns the texture info for this tile
    *  @return {TextureInfo}
    */
    getTextureInfo()
    { return textureInfos[this.textureIndex]; }
}

/** Texture Info - Stores info about each texture */
class TextureInfo
{
    /**
     * Create a TextureInfo, called automatically by the engine
     * @param {HTMLImageElement} image
     */
    constructor(image)
    {
        /** @property {HTMLImageElement} - image source */
        this.image = image;
        /** @property {Vector2} - size of the image */
        this.size = vec2(image.width, image.height);
        /** @property {WebGLTexture} - webgl texture */
        this.glTexture = glEnable && glCreateTexture(image);
        /** @property {Vector2} - size to adjust tile to fix bleeding */
        this.fixBleedSize = vec2(tileFixBleedScale).divide(this.size);
    }
}

///////////////////////////////////////////////////////////////////////////////

/** Convert from screen to world space coordinates
 *  @param {Vector2} screenPos
 *  @return {Vector2}
 *  @memberof Draw */
function screenToWorld(screenPos)
{
    return new Vector2
    (
        (screenPos.x - mainCanvasSize.x/2 + .5) /  cameraScale + cameraPos.x,
        (screenPos.y - mainCanvasSize.y/2 + .5) / -cameraScale + cameraPos.y
    );
}

/** Convert from world to screen space coordinates
 *  @param {Vector2} worldPos
 *  @return {Vector2}
 *  @memberof Draw */
function worldToScreen(worldPos)
{
    return new Vector2
    (
        (worldPos.x - cameraPos.x) *  cameraScale + mainCanvasSize.x/2 - .5,
        (worldPos.y - cameraPos.y) * -cameraScale + mainCanvasSize.y/2 - .5
    );
}

/** Get the camera's visible area in world space
 *  @return {Vector2}
 *  @memberof Draw */
function getCameraSize() { return mainCanvasSize.scale(1/cameraScale); }

/** Draw textured tile centered in world space, with color applied if using WebGL
 *  @param {Vector2} pos                        - Center of the tile in world space
 *  @param {Vector2} [size=(1,1)]               - Size of the tile in world space
 *  @param {TileInfo}[tileInfo]                 - Tile info to use, untextured if undefined
 *  @param {Color}   [color=(1,1,1,1)]          - Color to modulate with
 *  @param {Number}  [angle]                    - Angle to rotate by
 *  @param {Boolean} [mirror]                   - If true image is flipped along the Y axis
 *  @param {Color}   [additiveColor=(0,0,0,0)]  - Additive color to be applied
 *  @param {Boolean} [useWebGL=glEnable]        - Use accelerated WebGL rendering
 *  @param {Boolean} [screenSpace=false]        - If true the pos and size are in screen space
 *  @param {CanvasRenderingContext2D|OffscreenCanvasRenderingContext2D} [context] - Canvas 2D context to draw to
 *  @memberof Draw */
function drawTile(pos, size=vec2(1), tileInfo, color=new Color,
    angle=0, mirror, additiveColor=new Color(0,0,0,0), useWebGL=glEnable, screenSpace, context)
{
    ASSERT(!context || !useWebGL, 'context only supported in canvas 2D mode'); 
    ASSERT(typeof tileInfo !== 'number' || !tileInfo, 
        'this is an old style calls, to fix replace it with tile(tileIndex, tileSize)');

    const textureInfo = tileInfo && tileInfo.getTextureInfo();
    if (useWebGL)
    {
        if (screenSpace)
        {
            // convert to world space
            pos = screenToWorld(pos);
            size = size.scale(1/cameraScale);
        }
        
        if (textureInfo)
        {
            // calculate uvs and render
            const x = tileInfo.pos.x / textureInfo.size.x;
            const y = tileInfo.pos.y / textureInfo.size.y;
            const w = tileInfo.size.x / textureInfo.size.x;
            const h = tileInfo.size.y / textureInfo.size.y;
            const tileImageFixBleed = textureInfo.fixBleedSize;
            glSetTexture(textureInfo.glTexture);
            glDraw(pos.x, pos.y, mirror ? -size.x : size.x, size.y, angle, 
                x + tileImageFixBleed.x,     y + tileImageFixBleed.y, 
                x - tileImageFixBleed.x + w, y - tileImageFixBleed.y + h, 
                color.rgbaInt(), additiveColor.rgbaInt()); 
        }
        else
        {
            // if no tile info, force untextured
            glDraw(pos.x, pos.y, size.x, size.y, angle, 0, 0, 0, 0, 0, color.rgbaInt()); 
        }
    }
    else
    {
        // normal canvas 2D rendering method (slower)
        showWatermark && ++drawCount;
        drawCanvas2D(pos, size, angle, mirror, (context)=>
        {
            if (textureInfo)
            {
                // calculate uvs and render
                const x = tileInfo.pos.x + tileFixBleedScale;
                const y = tileInfo.pos.y + tileFixBleedScale;
                const w = tileInfo.size.x - 2*tileFixBleedScale;
                const h = tileInfo.size.y - 2*tileFixBleedScale;
                context.globalAlpha = color.a; // only alpha is supported
                context.drawImage(textureInfo.image, x, y, w, h, -.5, -.5, 1, 1);
                context.globalAlpha = 1; // set back to full alpha
            }
            else
            {
                // if no tile info, force untextured
                context.fillStyle = color;
                context.fillRect(-.5, -.5, 1, 1);
            }
        }, screenSpace, context);
    }
}

/** Draw colored rect centered on pos
 *  @param {Vector2} pos
 *  @param {Vector2} [size=(1,1)]
 *  @param {Color}   [color=(1,1,1,1)]
 *  @param {Number}  [angle]
 *  @param {Boolean} [useWebGL=glEnable]
 *  @param {Boolean} [screenSpace=false]
 *  @param {CanvasRenderingContext2D|OffscreenCanvasRenderingContext2D} [context]
 *  @memberof Draw */
function drawRect(pos, size, color, angle, useWebGL, screenSpace, context)
{ 
    drawTile(pos, size, undefined, color, angle, false, undefined, useWebGL, screenSpace, context); 
}

/** Draw colored line between two points
 *  @param {Vector2} posA
 *  @param {Vector2} posB
 *  @param {Number}  [thickness]
 *  @param {Color}   [color=(1,1,1,1)]
 *  @param {Boolean} [useWebGL=glEnable]
 *  @param {Boolean} [screenSpace=false]
 *  @param {CanvasRenderingContext2D|OffscreenCanvasRenderingContext2D} [context]
 *  @memberof Draw */
function drawLine(posA, posB, thickness=.1, color, useWebGL, screenSpace, context)
{
    const halfDelta = vec2((posB.x - posA.x)/2, (posB.y - posA.y)/2);
    const size = vec2(thickness, halfDelta.length()*2);
    drawRect(posA.add(halfDelta), size, color, halfDelta.angle(), useWebGL, screenSpace, context);
}

/** Draw directly to a 2d canvas context in world space
 *  @param {Vector2}  pos
 *  @param {Vector2}  size
 *  @param {Number}   angle
 *  @param {Boolean}  mirror
 *  @param {Function} drawFunction
 *  @param {Boolean} [screenSpace=false]
 *  @param {CanvasRenderingContext2D|OffscreenCanvasRenderingContext2D} [context=mainContext]
 *  @memberof Draw */
function drawCanvas2D(pos, size, angle, mirror, drawFunction, screenSpace, context=mainContext)
{
    if (!screenSpace)
    {
        // transform from world space to screen space
        pos = worldToScreen(pos);
        size = size.scale(cameraScale);
    }
    context.save();
    context.translate(pos.x+.5, pos.y+.5);
    context.rotate(angle);
    context.scale(mirror ? -size.x : size.x, -size.y);
    drawFunction(context);
    context.restore();
}

/** Enable normal or additive blend mode
 *  @param {Boolean} [additive]
 *  @param {Boolean} [useWebGL=glEnable]
 *  @param {CanvasRenderingContext2D|OffscreenCanvasRenderingContext2D} [context=mainContext]
 *  @memberof Draw */
function setBlendMode(additive, useWebGL=glEnable, context)
{
    ASSERT(!context || !useWebGL, 'context only supported in canvas 2D mode');
    if (useWebGL)
        glAdditive = additive;
    else
    {
        if (!context)
            context = mainContext;
        context.globalCompositeOperation = additive ? 'lighter' : 'source-over';
    }
}

/** Draw text on overlay canvas in world space
 *  Automatically splits new lines into rows
 *  @param {String}  text
 *  @param {Vector2} pos
 *  @param {Number}  [size]
 *  @param {Color}   [color=(1,1,1,1)]
 *  @param {Number}  [lineWidth]
 *  @param {Color}   [lineColor=(0,0,0,1)]
 *  @param {CanvasTextAlign}  [textAlign='center']
 *  @param {String}  [font=fontDefault]
 *  @param {CanvasRenderingContext2D|OffscreenCanvasRenderingContext2D} [context=overlayContext]
 *  @memberof Draw */
function drawText(text, pos, size=1, color, lineWidth=0, lineColor, textAlign, font, context)
{
    drawTextScreen(text, worldToScreen(pos), size*cameraScale, color, lineWidth*cameraScale, lineColor, textAlign, font, context);
}

/** Draw text on overlay canvas in screen space
 *  Automatically splits new lines into rows
 *  @param {String}  text
 *  @param {Vector2} pos
 *  @param {Number}  [size]
 *  @param {Color}   [color=(1,1,1,1)]
 *  @param {Number}  [lineWidth]
 *  @param {Color}   [lineColor=(0,0,0,1)]
 *  @param {CanvasTextAlign}  [textAlign]
 *  @param {String}  [font=fontDefault]
 *  @param {CanvasRenderingContext2D|OffscreenCanvasRenderingContext2D} [context=overlayContext]
 *  @memberof Draw */
function drawTextScreen(text, pos, size=1, color=new Color, lineWidth=0, lineColor=new Color(0,0,0), textAlign='center', font=fontDefault, context=overlayContext)
{
    context.fillStyle = color.toString();
    context.lineWidth = lineWidth;
    context.strokeStyle = lineColor.toString();
    context.textAlign = textAlign;
    context.font = size + 'px '+ font;
    context.textBaseline = 'middle';
    context.lineJoin = 'round';

    pos = pos.copy();
    (text+'').split('\n').forEach(line=>
    {
        lineWidth && context.strokeText(line, pos.x, pos.y);
        context.fillText(line, pos.x, pos.y);
        pos.y += size;
    });
}

///////////////////////////////////////////////////////////////////////////////

let engineFontImage;

/** 
 * Font Image Object - Draw text on a 2D canvas by using characters in an image
 * - 96 characters (from space to tilde) are stored in an image
 * - Uses a default 8x8 font if none is supplied
 * - You can also use fonts from the main tile sheet
 * @example
 * // use built in font
 * const font = new ImageFont;
 * 
 * // draw text
 * font.drawTextScreen("LittleJS\nHello World!", vec2(200, 50));
 */
class FontImage
{
    /** Create an image font
     *  @param {HTMLImageElement} [image]    - Image for the font, if undefined default font is used
     *  @param {Vector2} [tileSize=(8,8)]    - Size of the font source tiles
     *  @param {Vector2} [paddingSize=(0,1)] - How much extra space to add between characters
     *  @param {CanvasRenderingContext2D|OffscreenCanvasRenderingContext2D} [context=overlayContext] - context to draw to
     */
    constructor(image, tileSize=vec2(8), paddingSize=vec2(0,1), context=overlayContext)
    {
        // load default font image
        if (!engineFontImage)
            (engineFontImage = new Image).src = 'data:image/png;base64,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';

        this.image = image || engineFontImage;
        this.tileSize = tileSize;
        this.paddingSize = paddingSize;
        this.context = context;
    }

    /** Draw text in world space using the image font
     *  @param {String}  text
     *  @param {Vector2} pos
     *  @param {Number}  [scale=.25]
     *  @param {Boolean} [center]
     */
    drawText(text, pos, scale=1, center)
    {
        this.drawTextScreen(text, worldToScreen(pos).floor(), scale*cameraScale|0, center);
    }

    /** Draw text in screen space using the image font
     *  @param {String}  text
     *  @param {Vector2} pos
     *  @param {Number}  [scale]
     *  @param {Boolean} [center]
     */
    drawTextScreen(text, pos, scale=4, center)
    {
        const context = this.context;
        context.save();
        context.imageSmoothingEnabled = !canvasPixelated;

        const size = this.tileSize;
        const drawSize = size.add(this.paddingSize).scale(scale);
        const cols = this.image.width / this.tileSize.x |0;
        (text+'').split('\n').forEach((line, i)=>
        {
            const centerOffset = center ? line.length * size.x * scale / 2 |0 : 0;
            for(let j=line.length; j--;)
            {
                // draw each character
                let charCode = line[j].charCodeAt(0);
                if (charCode < 32 || charCode > 127)
                    charCode = 127; // unknown character

                // get the character source location and draw it
                const tile = charCode - 32;
                const x = tile % cols;
                const y = tile / cols |0;
                const drawPos = pos.add(vec2(j,i).multiply(drawSize));
                context.drawImage(this.image, x * size.x, y * size.y, size.x, size.y, 
                    drawPos.x - centerOffset, drawPos.y, size.x * scale, size.y * scale);
            }
        });

        context.restore();
    }
}

///////////////////////////////////////////////////////////////////////////////
// Fullscreen mode

/** Returns true if fullscreen mode is active
 *  @return {Boolean}
 *  @memberof Draw */
function isFullscreen() { return !!document.fullscreenElement; }

/** Toggle fullsceen mode
 *  @memberof Draw */
function toggleFullscreen()
{
    if (isFullscreen())
    {
        if (document.exitFullscreen)
            document.exitFullscreen();
    }
    else if (document.body.requestFullscreen)
            document.body.requestFullscreen();
}
/** 
 * LittleJS Input System
 * - Tracks keyboard down, pressed, and released
 * - Tracks mouse buttons, position, and wheel
 * - Tracks multiple analog gamepads
 * - Touch input is handled as mouse input
 * - Virtual gamepad for touch devices
 * @namespace Input
 */



/** Returns true if device key is down
 *  @param {String|Number} key
 *  @param {Number} [device]
 *  @return {Boolean}
 *  @memberof Input */
function keyIsDown(key, device=0)
{ 
    ASSERT(device > 0 || typeof key !== 'number' || key < 3, 'use code string for keyboard');
    return inputData[device] && !!(inputData[device][key] & 1); 
}

/** Returns true if device key was pressed this frame
 *  @param {String|Number} key
 *  @param {Number} [device]
 *  @return {Boolean}
 *  @memberof Input */
function keyWasPressed(key, device=0)
{ 
    ASSERT(device > 0 || typeof key !== 'number' || key < 3, 'use code string for keyboard');
    return inputData[device] && !!(inputData[device][key] & 2); 
}

/** Returns true if device key was released this frame
 *  @param {String|Number} key
 *  @param {Number} [device]
 *  @return {Boolean}
 *  @memberof Input */
function keyWasReleased(key, device=0)
{ 
    ASSERT(device > 0 || typeof key !== 'number' || key < 3, 'use code string for keyboard');
    return inputData[device] && !!(inputData[device][key] & 4);
}

/** Clears all input
 *  @memberof Input */
function clearInput() { inputData = [[]]; }

/** Returns true if mouse button is down
 *  @function
 *  @param {Number} button
 *  @return {Boolean}
 *  @memberof Input */
const mouseIsDown = keyIsDown;

/** Returns true if mouse button was pressed
 *  @function
 *  @param {Number} button
 *  @return {Boolean}
 *  @memberof Input */
const mouseWasPressed = keyWasPressed;

/** Returns true if mouse button was released
 *  @function
 *  @param {Number} button
 *  @return {Boolean}
 *  @memberof Input */
const mouseWasReleased = keyWasReleased;

/** Mouse pos in world space
 *  @type {Vector2}
 *  @memberof Input */
let mousePos = vec2();

/** Mouse pos in screen space
 *  @type {Vector2}
 *  @memberof Input */
let mousePosScreen = vec2();

/** Mouse wheel delta this frame
 *  @type {Number}
 *  @memberof Input */
let mouseWheel = 0;

/** Returns true if user is using gamepad (has more recently pressed a gamepad button)
 *  @type {Boolean}
 *  @memberof Input */
let isUsingGamepad = false;

/** Prevents input continuing to the default browser handling (false by default)
 *  @type {Boolean}
 *  @memberof Input */
let preventDefaultInput = false;

/** Returns true if gamepad button is down
 *  @param {Number} button
 *  @param {Number} [gamepad]
 *  @return {Boolean}
 *  @memberof Input */
function gamepadIsDown(button, gamepad=0)
{ return keyIsDown(button, gamepad+1); }

/** Returns true if gamepad button was pressed
 *  @param {Number} button
 *  @param {Number} [gamepad]
 *  @return {Boolean}
 *  @memberof Input */
function gamepadWasPressed(button, gamepad=0)
{ return keyWasPressed(button, gamepad+1); }

/** Returns true if gamepad button was released
 *  @param {Number} button
 *  @param {Number} [gamepad]
 *  @return {Boolean}
 *  @memberof Input */
function gamepadWasReleased(button, gamepad=0)
{ return keyWasReleased(button, gamepad+1); }

/** Returns gamepad stick value
 *  @param {Number} stick
 *  @param {Number} [gamepad]
 *  @return {Vector2}
 *  @memberof Input */
function gamepadStick(stick,  gamepad=0)
{ return gamepadStickData[gamepad] ? gamepadStickData[gamepad][stick] || vec2() : vec2(); }

///////////////////////////////////////////////////////////////////////////////
// Input update called by engine

// store input as a bit field for each key: 1 = isDown, 2 = wasPressed, 4 = wasReleased
// mouse and keyboard are stored together in device 0, gamepads are in devices > 0
let inputData = [[]];

function inputUpdate()
{
    if (headlessMode) return;

    // clear input when lost focus (prevent stuck keys)
    if(!(touchInputEnable && isTouchDevice) && !document.hasFocus())
        clearInput();

    // update mouse world space position
    mousePos = screenToWorld(mousePosScreen);

    // update gamepads if enabled
    gamepadsUpdate();
}

function inputUpdatePost()
{
    if (headlessMode) return;

    // clear input to prepare for next frame
    for (const deviceInputData of inputData)
    for (const i in deviceInputData)
        deviceInputData[i] &= 1;
    mouseWheel = 0;
}

///////////////////////////////////////////////////////////////////////////////
// Input event handlers

function inputInit()
{
    if (headlessMode) return;

    onkeydown = (e)=>
    {
        if (debug && e.target != document.body) return;
        if (!e.repeat)
        {
            isUsingGamepad = false;
            inputData[0][e.code] = 3;
            if (inputWASDEmulateDirection)
                inputData[0][remapKey(e.code)] = 3;
        }
        preventDefaultInput && e.preventDefault();
    }

    onkeyup = (e)=>
    {
        if (debug && e.target != document.body) return;
        inputData[0][e.code] = 4;
        if (inputWASDEmulateDirection)
            inputData[0][remapKey(e.code)] = 4;
    }

    // handle remapping wasd keys to directions
    function remapKey(c)
    {
        return inputWASDEmulateDirection ? 
            c == 'KeyW' ? 'ArrowUp' : 
            c == 'KeyS' ? 'ArrowDown' : 
            c == 'KeyA' ? 'ArrowLeft' : 
            c == 'KeyD' ? 'ArrowRight' : c : c;
    }
    
    // mouse event handlers
    onmousedown   = (e)=>
    {
        // fix stalled audio requiring user interaction
        if (soundEnable && !headlessMode && audioContext && audioContext.state != 'running')
            audioContext.resume();
        
        isUsingGamepad = false; 
        inputData[0][e.button] = 3; 
        mousePosScreen = mouseToScreen(e); 
        e.button && e.preventDefault();
    }
    onmouseup     = (e)=> inputData[0][e.button] = inputData[0][e.button] & 2 | 4;
    onmousemove   = (e)=> mousePosScreen = mouseToScreen(e);
    onwheel       = (e)=> mouseWheel = e.ctrlKey ? 0 : sign(e.deltaY);
    oncontextmenu = (e)=> false; // prevent right click menu

    // init touch input
    if (isTouchDevice && touchInputEnable)
        touchInputInit();
}

// convert a mouse or touch event position to screen space
function mouseToScreen(mousePos)
{
    if (!mainCanvas || headlessMode)
        return vec2(); // fix bug that can occur if user clicks before page loads

    const rect = mainCanvas.getBoundingClientRect();
    return vec2(mainCanvas.width, mainCanvas.height).multiply(
        vec2(percent(mousePos.x, rect.left, rect.right), percent(mousePos.y, rect.top, rect.bottom)));
}

///////////////////////////////////////////////////////////////////////////////
// Gamepad input

// gamepad internal variables
const gamepadStickData = [];

// gamepads are updated by engine every frame automatically
function gamepadsUpdate()
{
    const applyDeadZones = (v)=>
    {
        const min=.3, max=.8;
        const deadZone = (v)=> 
            v >  min ?  percent( v, min, max) : 
            v < -min ? -percent(-v, min, max) : 0;
        return vec2(deadZone(v.x), deadZone(-v.y)).clampLength();
    }

    // update touch gamepad if enabled
    if (touchGamepadEnable && isTouchDevice)
    {
        ASSERT(touchGamepadButtons, 'set touchGamepadEnable before calling init!');
        if (touchGamepadTimer.isSet())
        {
            // read virtual analog stick
            const sticks = gamepadStickData[0] || (gamepadStickData[0] = []);
            sticks[0] = vec2();
            if (touchGamepadAnalog)
                sticks[0] = applyDeadZones(touchGamepadStick);
            else if (touchGamepadStick.lengthSquared() > .3)
            {
                // convert to 8 way dpad
                sticks[0].x = Math.round(touchGamepadStick.x);
                sticks[0].y = -Math.round(touchGamepadStick.y);
                sticks[0] = sticks[0].clampLength();
            }

            // read virtual gamepad buttons
            const data = inputData[1] || (inputData[1] = []);
            for (let i=10; i--;)
            {
                const j = i == 3 ? 2 : i == 2 ? 3 : i; // fix button locations
                const wasDown = gamepadIsDown(j,0);
                data[j] = touchGamepadButtons[i] ? wasDown ? 1 : 3 : wasDown ? 4 : 0;
            }
        }
    }

    // return if gamepads are disabled or not supported
    if (!gamepadsEnable || !navigator || !navigator.getGamepads)
        return;

    // only poll gamepads when focused or in debug mode
    if (!debug && !document.hasFocus())
        return;

    // poll gamepads
    const gamepads = navigator.getGamepads();
    for (let i = gamepads.length; i--;)
    {
        // get or create gamepad data
        const gamepad = gamepads[i];
        const data = inputData[i+1] || (inputData[i+1] = []);
        const sticks = gamepadStickData[i] || (gamepadStickData[i] = []);

        if (gamepad)
        {
            // read analog sticks
            for (let j = 0; j < gamepad.axes.length-1; j+=2)
                sticks[j>>1] = applyDeadZones(vec2(gamepad.axes[j],gamepad.axes[j+1]));
            
            // read buttons
            for (let j = gamepad.buttons.length; j--;)
            {
                const button = gamepad.buttons[j];
                const wasDown = gamepadIsDown(j,i);
                data[j] = button.pressed ? wasDown ? 1 : 3 : wasDown ? 4 : 0;
                isUsingGamepad ||= !i && button.pressed;
            }

            if (gamepadDirectionEmulateStick)
            {
                // copy dpad to left analog stick when pressed
                const dpad = vec2(
                    (gamepadIsDown(15,i)&&1) - (gamepadIsDown(14,i)&&1), 
                    (gamepadIsDown(12,i)&&1) - (gamepadIsDown(13,i)&&1));
                if (dpad.lengthSquared())
                    sticks[0] = dpad.clampLength();
            }

            // disable touch gamepad if using real gamepad
            touchGamepadEnable && isUsingGamepad && touchGamepadTimer.unset(); 
        }
    }
}

///////////////////////////////////////////////////////////////////////////////

/** Pulse the vibration hardware if it exists
 *  @param {Number|Array} [pattern] - single value in ms or vibration interval array
 *  @memberof Input */
function vibrate(pattern=100)
{ vibrateEnable && !headlessMode && navigator && navigator.vibrate && navigator.vibrate(pattern); }

/** Cancel any ongoing vibration
 *  @memberof Input */
function vibrateStop() { vibrate(0); }

///////////////////////////////////////////////////////////////////////////////
// Touch input & virtual on screen gamepad

/** True if a touch device has been detected
 *  @memberof Input */
const isTouchDevice = window.ontouchstart !== undefined;

// touch gamepad internal variables
let touchGamepadTimer = new Timer, touchGamepadButtons, touchGamepadStick;

// enable touch input mouse passthrough
function touchInputInit()
{
    // add non passive touch event listeners
    let handleTouch = handleTouchDefault;
    if (touchGamepadEnable)
    {
        // touch input internal variables
        handleTouch = handleTouchGamepad;
        touchGamepadButtons = [];
        touchGamepadStick = vec2();
    }
    document.addEventListener('touchstart', (e) => handleTouch(e), { passive: false });
    document.addEventListener('touchmove',  (e) => handleTouch(e), { passive: false });
    document.addEventListener('touchend',   (e) => handleTouch(e), { passive: false });

    // override mouse events
    onmousedown = onmouseup = ()=> 0;

    // handle all touch events the same way
    let wasTouching;
    function handleTouchDefault(e)
    {
        // fix stalled audio requiring user interaction
        if (soundEnable && !headlessMode && audioContext && audioContext.state != 'running')
            audioContext.resume();

        // check if touching and pass to mouse events
        const touching = e.touches.length;
        const button = 0; // all touches are left mouse button
        if (touching)
        {
            // set event pos and pass it along
            const p = vec2(e.touches[0].clientX, e.touches[0].clientY);
            mousePosScreen = mouseToScreen(p);
            wasTouching ? isUsingGamepad = false : inputData[0][button] = 3;
        }
        else if (wasTouching)
            inputData[0][button] = inputData[0][button] & 2 | 4;

        // set was touching
        wasTouching = touching;

        // prevent default handling like copy and magnifier lens
        if (document.hasFocus()) // allow document to get focus
            e.preventDefault();
        
        // must return true so the document will get focus
        return true;
    }

    // special handling for virtual gamepad mode
    function handleTouchGamepad(e)
    {
        // clear touch gamepad input
        touchGamepadStick = vec2();
        touchGamepadButtons = [];
        isUsingGamepad = true;
            
        const touching = e.touches.length;
        if (touching)
        {
            touchGamepadTimer.set();
            if (paused)
            {
                // touch anywhere to press start when paused
                touchGamepadButtons[9] = 1;
                return;
            }
        }

        // get center of left and right sides
        const stickCenter = vec2(touchGamepadSize, mainCanvasSize.y-touchGamepadSize);
        const buttonCenter = mainCanvasSize.subtract(vec2(touchGamepadSize, touchGamepadSize));
        const startCenter = mainCanvasSize.scale(.5);

        // check each touch point
        for (const touch of e.touches)
        {
            const touchPos = mouseToScreen(vec2(touch.clientX, touch.clientY));
            if (touchPos.distance(stickCenter) < touchGamepadSize)
            {
                // virtual analog stick
                touchGamepadStick = touchPos.subtract(stickCenter).scale(2/touchGamepadSize).clampLength();
            }
            else if (touchPos.distance(buttonCenter) < touchGamepadSize)
            {
                // virtual face buttons
                const button = touchPos.subtract(buttonCenter).direction();
                touchGamepadButtons[button] = 1;
            }
            else if (touchPos.distance(startCenter) < touchGamepadSize)
            {
                // virtual start button in center
                touchGamepadButtons[9] = 1;
            }
        }

        // call default touch handler so normal touch events still work
        handleTouchDefault(e);
        
        // must return true so the document will get focus
        return true;
    }
}

// render the touch gamepad, called automatically by the engine
function touchGamepadRender()
{
    if (!touchInputEnable || !isTouchDevice || headlessMode) return;
    if (!touchGamepadEnable || !touchGamepadTimer.isSet())
        return;
    
    // fade off when not touching or paused
    const alpha = percent(touchGamepadTimer.get(), 4, 3);
    if (!alpha || paused)
        return;

    // setup the canvas
    const context = overlayContext;
    context.save();
    context.globalAlpha = alpha*touchGamepadAlpha;
    context.strokeStyle = '#fff';
    context.lineWidth = 3;

    // draw left analog stick
    context.fillStyle = touchGamepadStick.lengthSquared() > 0 ? '#fff' : '#000';
    context.beginPath();

    const leftCenter = vec2(touchGamepadSize, mainCanvasSize.y-touchGamepadSize);
    if (touchGamepadAnalog) // draw circle shaped gamepad
    {
        context.arc(leftCenter.x, leftCenter.y, touchGamepadSize/2, 0, 9);
        context.fill();
        context.stroke();
    }
    else // draw cross shaped gamepad
    {
        for(let i=10; i--;)
        {
            const angle = i*PI/4;
            context.arc(leftCenter.x, leftCenter.y,touchGamepadSize*.6, angle + PI/8, angle + PI/8);
            i%2 && context.arc(leftCenter.x, leftCenter.y, touchGamepadSize*.33, angle, angle);
            i==1 && context.fill();
        }
        context.stroke();
    }
    
    // draw right face buttons
    const rightCenter = vec2(mainCanvasSize.x-touchGamepadSize, mainCanvasSize.y-touchGamepadSize);
    for (let i=4; i--;)
    {
        const pos = rightCenter.add(vec2().setDirection(i, touchGamepadSize/2));
        context.fillStyle = touchGamepadButtons[i] ? '#fff' : '#000';
        context.beginPath();
        context.arc(pos.x, pos.y, touchGamepadSize/4, 0,9);
        context.fill();
        context.stroke();
    }

    // set canvas back to normal
    context.restore();
}
/** 
 * LittleJS Audio System
 * - <a href=https://killedbyapixel.github.io/ZzFX/>ZzFX Sound Effects</a> - ZzFX Sound Effect Generator
 * - <a href=https://keithclark.github.io/ZzFXM/>ZzFXM Music</a> - ZzFXM Music System
 * - Caches sounds and music for fast playback
 * - Can attenuate and apply stereo panning to sounds
 * - Ability to play mp3, ogg, and wave files
 * - Speech synthesis functions
 * @namespace Audio
 */



/** Audio context used by the engine
 *  @type {AudioContext}
 *  @memberof Audio */
let audioContext;

/** Master gain node for all audio to pass through
 *  @type {GainNode}
 *  @memberof Audio */
let audioGainNode;

function audioInit()
{
    if (!soundEnable || headlessMode) return;
    
    // create audio context
    audioContext = new AudioContext;

    // create and connect gain node
    // (createGain is more widely spported then GainNode construtor)
    audioGainNode = audioContext.createGain();
    audioGainNode.connect(audioContext.destination);
    setSoundVolume(soundVolume); // update gain volume
}

///////////////////////////////////////////////////////////////////////////////

/** 
 * Sound Object - Stores a sound for later use and can be played positionally
 * 
 * <a href=https://killedbyapixel.github.io/ZzFX/>Create sounds using the ZzFX Sound Designer.</a>
 * @example
 * // create a sound
 * const sound_example = new Sound([.5,.5]);
 * 
 * // play the sound
 * sound_example.play();
 */
class Sound
{
    /** Create a sound object and cache the zzfx samples for later use
     *  @param {Array}  zzfxSound - Array of zzfx parameters, ex. [.5,.5]
     *  @param {Number} [range=soundDefaultRange] - World space max range of sound, will not play if camera is farther away
     *  @param {Number} [taper=soundDefaultTaper] - At what percentage of range should it start tapering
     */
    constructor(zzfxSound, range=soundDefaultRange, taper=soundDefaultTaper)
    {
        if (!soundEnable || headlessMode) return;

        /** @property {Number} - World space max range of sound, will not play if camera is farther away */
        this.range = range;

        /** @property {Number} - At what percentage of range should it start tapering off */
        this.taper = taper;

        /** @property {Number} - How much to randomize frequency each time sound plays */
        this.randomness = 0;

        if (zzfxSound)
        {
            // generate zzfx sound now for fast playback
            const defaultRandomness = .05;
            this.randomness = zzfxSound[1] || defaultRandomness;
            zzfxSound[1] = 0; // generate without randomness
            this.sampleChannels = [zzfxG(...zzfxSound)];
            this.sampleRate = zzfxR;
        }
    }

    /** Play the sound
     *  @param {Vector2} [pos] - World space position to play the sound, sound is not attenuated if null
     *  @param {Number}  [volume] - How much to scale volume by (in addition to range fade)
     *  @param {Number}  [pitch] - How much to scale pitch by (also adjusted by this.randomness)
     *  @param {Number}  [randomnessScale] - How much to scale randomness
     *  @param {Boolean} [loop] - Should the sound loop
     *  @return {AudioBufferSourceNode} - The audio source node
     */
    play(pos, volume=1, pitch=1, randomnessScale=1, loop=false)
    {
        if (!soundEnable || headlessMode) return;
        if (!this.sampleChannels) return;

        let pan;
        if (pos)
        {
            const range = this.range;
            if (range)
            {
                // apply range based fade
                const lengthSquared = cameraPos.distanceSquared(pos);
                if (lengthSquared > range*range)
                    return; // out of range

                // attenuate volume by distance
                volume *= percent(lengthSquared**.5, range, range*this.taper);
            }

            // get pan from screen space coords
            pan = worldToScreen(pos).x * 2/mainCanvas.width - 1;
        }

        // play the sound
        const playbackRate = pitch + pitch * this.randomness*randomnessScale*rand(-1,1);
        this.gainNode = audioContext.createGain();
        return this.source = playSamples(this.sampleChannels, volume, playbackRate, pan, loop, this.sampleRate, this.gainNode);
    }

    /** Set the sound volume
     *  @param {Number}  [volume] - How much to scale volume by
     */
    setVolume(volume=1)
    {
        if (this.gainNode)
            this.gainNode.gain.value = volume;
    }

    /** Stop the last instance of this sound that was played */
    stop()
    {
        if (this.source)
            this.source.stop();
        this.source = undefined;
    }
    
    /** Get source of most recent instance of this sound that was played
     *  @return {AudioBufferSourceNode}
     */
    getSource() { return this.source; }

    /** Play the sound as a note with a semitone offset
     *  @param {Number}  semitoneOffset - How many semitones to offset pitch
     *  @param {Vector2} [pos] - World space position to play the sound, sound is not attenuated if null
     *  @param {Number}  [volume=1] - How much to scale volume by (in addition to range fade)
     *  @return {AudioBufferSourceNode} - The audio source node
     */
    playNote(semitoneOffset, pos, volume)
    { return this.play(pos, volume, 2**(semitoneOffset/12), 0); }

    /** Get how long this sound is in seconds
     *  @return {Number} - How long the sound is in seconds (undefined if loading)
     */
    getDuration() 
    { return this.sampleChannels && this.sampleChannels[0].length / this.sampleRate; }
    
    /** Check if sound is loading, for sounds fetched from a url
     *  @return {Boolean} - True if sound is loading and not ready to play
     */
    isLoading() { return !this.sampleChannels; }
}

/** 
 * Sound Wave Object - Stores a wave sound for later use and can be played positionally
 * - this can be used to play wave, mp3, and ogg files
 * @example
 * // create a sound
 * const sound_example = new SoundWave('sound.mp3');
 * 
 * // play the sound
 * sound_example.play();
 */
class SoundWave extends Sound
{
    /** Create a sound object and cache the wave file for later use
     *  @param {String} filename - Filename of audio file to load
     *  @param {Number} [randomness] - How much to randomize frequency each time sound plays
     *  @param {Number} [range=soundDefaultRange] - World space max range of sound, will not play if camera is farther away
     *  @param {Number} [taper=soundDefaultTaper] - At what percentage of range should it start tapering off
     *  @param {Function} [onloadCallback] - callback function to call when sound is loaded
     */
    constructor(filename, randomness=0, range, taper, onloadCallback)
    {
        super(undefined, range, taper);
        if (!soundEnable || headlessMode) return;

        this.randomness = randomness;
        fetch(filename)
        .then(response => response.arrayBuffer())
        .then(arrayBuffer => audioContext.decodeAudioData(arrayBuffer))
        .then(audioBuffer => 
        {
            this.sampleChannels = [];
            for (let i = audioBuffer.numberOfChannels; i--;)
                this.sampleChannels[i] = Array.from(audioBuffer.getChannelData(i));
            this.sampleRate = audioBuffer.sampleRate;
        }).then(() => onloadCallback && onloadCallback(this));
    }
}

/** Play an mp3, ogg, or wav audio from a local file or url
 *  @param {String}  filename - Location of sound file to play
 *  @param {Number}  [volume] - How much to scale volume by
 *  @param {Boolean} [loop] - True if the music should loop
 *  @return {SoundWave} - The sound object for this file
 *  @memberof Audio */
function playAudioFile(filename, volume=1, loop=false)
{
    if (!soundEnable || headlessMode) return;

    return new SoundWave(filename,0,0,0, s=>s.play(undefined, volume, 1, 1, loop));
}

/**
 * Music Object - Stores a zzfx music track for later use
 * 
 * <a href=https://keithclark.github.io/ZzFXM/>Create music with the ZzFXM tracker.</a>
 * @example
 * // create some music
 * const music_example = new Music(
 * [
 *     [                         // instruments
 *       [,0,400]                // simple note
 *     ], 
 *     [                         // patterns
 *         [                     // pattern 1
 *             [                 // channel 0
 *                 0, -1,        // instrument 0, left speaker
 *                 1, 0, 9, 1    // channel notes
 *             ], 
 *             [                 // channel 1
 *                 0, 1,         // instrument 0, right speaker
 *                 0, 12, 17, -1 // channel notes
 *             ]
 *         ],
 *     ],
 *     [0, 0, 0, 0], // sequence, play pattern 0 four times
 *     90            // BPM
 * ]);
 * 
 * // play the music
 * music_example.play();
 */
class Music extends Sound
{
    /** Create a music object and cache the zzfx music samples for later use
     *  @param {[Array, Array, Array, Number]} zzfxMusic - Array of zzfx music parameters
     */
    constructor(zzfxMusic)
    {
        super(undefined);

        if (!soundEnable || headlessMode) return;
        this.randomness = 0;
        this.sampleChannels = zzfxM(...zzfxMusic);
        this.sampleRate = zzfxR;
    }

    /** Play the music
     *  @param {Number}  [volume=1] - How much to scale volume by
     *  @param {Boolean} [loop] - True if the music should loop
     *  @return {AudioBufferSourceNode} - The audio source node
     */
    playMusic(volume, loop=false)
    { return super.play(undefined, volume, 1, 1, loop); }
}

/** Speak text with passed in settings
 *  @param {String} text - The text to speak
 *  @param {String} [language] - The language/accent to use (examples: en, it, ru, ja, zh)
 *  @param {Number} [volume] - How much to scale volume by
 *  @param {Number} [rate] - How quickly to speak
 *  @param {Number} [pitch] - How much to change the pitch by
 *  @return {SpeechSynthesisUtterance} - The utterance that was spoken
 *  @memberof Audio */
function speak(text, language='', volume=1, rate=1, pitch=1)
{
    if (!soundEnable || headlessMode) return;
    if (!speechSynthesis) return;

    // common languages (not supported by all browsers)
    // en - english,  it - italian, fr - french,  de - german, es - spanish
    // ja - japanese, ru - russian, zh - chinese, hi - hindi,  ko - korean

    // build utterance and speak
    const utterance = new SpeechSynthesisUtterance(text);
    utterance.lang = language;
    utterance.volume = 2*volume*soundVolume;
    utterance.rate = rate;
    utterance.pitch = pitch;
    speechSynthesis.speak(utterance);
    return utterance;
}

/** Stop all queued speech
 *  @memberof Audio */
function speakStop() {speechSynthesis && speechSynthesis.cancel();}

/** Get frequency of a note on a musical scale
 *  @param {Number} semitoneOffset - How many semitones away from the root note
 *  @param {Number} [rootFrequency=220] - Frequency at semitone offset 0
 *  @return {Number} - The frequency of the note
 *  @memberof Audio */
function getNoteFrequency(semitoneOffset, rootFrequency=220)
{ return rootFrequency * 2**(semitoneOffset/12); }

///////////////////////////////////////////////////////////////////////////////

/** Play cached audio samples with given settings
 *  @param {Array}    sampleChannels - Array of arrays of samples to play (for stereo playback)
 *  @param {Number}   [volume] - How much to scale volume by
 *  @param {Number}   [rate] - The playback rate to use
 *  @param {Number}   [pan] - How much to apply stereo panning
 *  @param {Boolean}  [loop] - True if the sound should loop when it reaches the end
 *  @param {Number}   [sampleRate=44100] - Sample rate for the sound
 *  @param {GainNode} [gainNode] - Optional gain node for volume control while playing
 *  @return {AudioBufferSourceNode} - The audio node of the sound played
 *  @memberof Audio */
function playSamples(sampleChannels, volume=1, rate=1, pan=0, loop=false, sampleRate=zzfxR, gainNode) 
{
    if (!soundEnable || headlessMode) return;

    // prevent sounds from building up if they can't be played
    if (audioContext.state != 'running')
    {
        // fix stalled audio
        audioContext.resume().then(()=>
            playSamples(sampleChannels, volume, rate, pan, loop, sampleRate, gainNode));

        // prevent suspended sounds from building up
        return;
    }

    // create buffer and source
    const channelCount = sampleChannels.length;
    const sampleLength = sampleChannels[0].length;
    const buffer = audioContext.createBuffer(channelCount, sampleLength, sampleRate);
    const source = audioContext.createBufferSource();

    // copy samples to buffer and setup source
    sampleChannels.forEach((c,i)=> buffer.getChannelData(i).set(c));
    source.buffer = buffer;
    source.playbackRate.value = rate;
    source.loop = loop;

    // create and connect gain node
    gainNode = gainNode || audioContext.createGain();
    gainNode.gain.value = volume;
    gainNode.connect(audioGainNode);

    // connect source to stereo panner and gain
    const pannerNode = new StereoPannerNode(audioContext, {'pan':clamp(pan, -1, 1)});
    source.connect(pannerNode).connect(gainNode);

    // play and return sound
    source.start();
    return source;
}

///////////////////////////////////////////////////////////////////////////////
// ZzFXMicro - Zuper Zmall Zound Zynth - v1.3.1 by Frank Force

/** Generate and play a ZzFX sound
 *  
 *  <a href=https://killedbyapixel.github.io/ZzFX/>Create sounds using the ZzFX Sound Designer.</a>
 *  @param {Array} zzfxSound - Array of ZzFX parameters, ex. [.5,.5]
 *  @return {AudioBufferSourceNode} - The audio node of the sound played
 *  @memberof Audio */
function zzfx(...zzfxSound) { return playSamples([zzfxG(...zzfxSound)]); }

/** Sample rate used for all ZzFX sounds
 *  @default 44100
 *  @memberof Audio */
const zzfxR = 44100; 

/** Generate samples for a ZzFX sound
 *  @param {Number}  [volume] - Volume scale (percent)
 *  @param {Number}  [randomness] - How much to randomize frequency (percent Hz)
 *  @param {Number}  [frequency] - Frequency of sound (Hz)
 *  @param {Number}  [attack] - Attack time, how fast sound starts (seconds)
 *  @param {Number}  [sustain] - Sustain time, how long sound holds (seconds)
 *  @param {Number}  [release] - Release time, how fast sound fades out (seconds)
 *  @param {Number}  [shape] - Shape of the sound wave
 *  @param {Number}  [shapeCurve] - Squarenes of wave (0=square, 1=normal, 2=pointy)
 *  @param {Number}  [slide] - How much to slide frequency (kHz/s)
 *  @param {Number}  [deltaSlide] - How much to change slide (kHz/s/s)
 *  @param {Number}  [pitchJump] - Frequency of pitch jump (Hz)
 *  @param {Number}  [pitchJumpTime] - Time of pitch jump (seconds)
 *  @param {Number}  [repeatTime] - Resets some parameters periodically (seconds)
 *  @param {Number}  [noise] - How much random noise to add (percent)
 *  @param {Number}  [modulation] - Frequency of modulation wave, negative flips phase (Hz)
 *  @param {Number}  [bitCrush] - Resamples at a lower frequency in (samples*100)
 *  @param {Number}  [delay] - Overlap sound with itself for reverb and flanger effects (seconds)
 *  @param {Number}  [sustainVolume] - Volume level for sustain (percent)
 *  @param {Number}  [decay] - Decay time, how long to reach sustain after attack (seconds)
 *  @param {Number}  [tremolo] - Trembling effect, rate controlled by repeat time (precent)
 *  @param {Number}  [filter] - Filter cutoff frequency, positive for HPF, negative for LPF (Hz)
 *  @return {Array} - Array of audio samples
 *  @memberof Audio
 */
function zzfxG
(
    // parameters
    volume = 1, randomness = .05, frequency = 220, attack = 0, sustain = 0,
    release = .1, shape = 0, shapeCurve = 1, slide = 0, deltaSlide = 0,
    pitchJump = 0, pitchJumpTime = 0, repeatTime = 0, noise = 0, modulation = 0,
    bitCrush = 0, delay = 0, sustainVolume = 1, decay = 0, tremolo = 0, filter = 0
)
{
    // LJS Note: ZZFX modded so randomness is handled by Sound class

    // init parameters
    let PI2 = PI*2, sampleRate = zzfxR,
        startSlide = slide *= 500 * PI2 / sampleRate / sampleRate,
        startFrequency = frequency *= 
            rand(1 + randomness, 1-randomness) * PI2 / sampleRate,
        b = [], t = 0, tm = 0, i = 0, j = 1, r = 0, c = 0, s = 0, f, length,

        // biquad LP/HP filter
        quality = 2, w = PI2 * abs(filter) * 2 / sampleRate,
        cos = Math.cos(w), alpha = Math.sin(w) / 2 / quality,
        a0 = 1 + alpha, a1 = -2*cos / a0, a2 = (1 - alpha) / a0,
        b0 = (1 + sign(filter) * cos) / 2 / a0, 
        b1 = -(sign(filter) + cos) / a0, b2 = b0,
        x2 = 0, x1 = 0, y2 = 0, y1 = 0;

    // scale by sample rate
    attack = attack * sampleRate + 9; // minimum attack to prevent pop
    decay *= sampleRate;
    sustain *= sampleRate;
    release *= sampleRate;
    delay *= sampleRate;
    deltaSlide *= 500 * PI2 / sampleRate**3;
    modulation *= PI2 / sampleRate;
    pitchJump *= PI2 / sampleRate;
    pitchJumpTime *= sampleRate;
    repeatTime = repeatTime * sampleRate | 0;

    // generate waveform
    for(length = attack + decay + sustain + release + delay | 0;
        i < length; b[i++] = s * volume)               // sample
    {
        if (!(++c%(bitCrush*100|0)))                   // bit crush
        {
            s = shape? shape>1? shape>2? shape>3?      // wave shape
                Math.sin(t**3) :                       // 4 noise
                clamp(Math.tan(t),1,-1):               // 3 tan
                1-(2*t/PI2%2+2)%2:                     // 2 saw
                1-4*abs(Math.round(t/PI2)-t/PI2):      // 1 triangle
                Math.sin(t);                           // 0 sin

            s = (repeatTime ?
                    1 - tremolo + tremolo*Math.sin(PI2*i/repeatTime) // tremolo
                    : 1) *
                sign(s)*(abs(s)**shapeCurve) *           // curve
                (i < attack ? i/attack :                 // attack
                i < attack + decay ?                     // decay
                1-((i-attack)/decay)*(1-sustainVolume) : // decay falloff
                i < attack  + decay + sustain ?          // sustain
                sustainVolume :                          // sustain volume
                i < length - delay ?                     // release
                (length - i - delay)/release *           // release falloff
                sustainVolume :                          // release volume
                0);                                      // post release

            s = delay ? s/2 + (delay > i ? 0 :           // delay
                (i<length-delay? 1 : (length-i)/delay) * // release delay 
                b[i-delay|0]/2/volume) : s;              // sample delay

            if (filter)                                   // apply filter
                s = y1 = b2*x2 + b1*(x2=x1) + b0*(x1=s) - a2*y2 - a1*(y2=y1);
        }

        f = (frequency += slide += deltaSlide) *// frequency
            Math.cos(modulation*tm++);          // modulation
        t += f + f*noise*Math.sin(i**5);        // noise

        if (j && ++j > pitchJumpTime)           // pitch jump
        { 
            frequency += pitchJump;             // apply pitch jump
            startFrequency += pitchJump;        // also apply to start
            j = 0;                              // stop pitch jump time
        } 

        if (repeatTime && !(++r % repeatTime))  // repeat
        { 
            frequency = startFrequency;         // reset frequency
            slide = startSlide;                 // reset slide
            j = j || 1;                         // reset pitch jump time
        }
    }

    return b;
}

///////////////////////////////////////////////////////////////////////////////
// ZzFX Music Renderer v2.0.3 by Keith Clark and Frank Force

/** Generate samples for a ZzFM song with given parameters
 *  @param {Array} instruments - Array of ZzFX sound paramaters
 *  @param {Array} patterns - Array of pattern data
 *  @param {Array} sequence - Array of pattern indexes
 *  @param {Number} [BPM] - Playback speed of the song in BPM
 *  @return {Array} - Left and right channel sample data
 *  @memberof Audio */
function zzfxM(instruments, patterns, sequence, BPM = 125) 
{
  let i, j, k;
  let instrumentParameters;
  let note;
  let sample;
  let patternChannel;
  let notFirstBeat;
  let stop;
  let instrument;
  let attenuation;
  let outSampleOffset;
  let isSequenceEnd;
  let sampleOffset = 0;
  let nextSampleOffset;
  let sampleBuffer = [];
  let leftChannelBuffer = [];
  let rightChannelBuffer = [];
  let channelIndex = 0;
  let panning = 0;
  let hasMore = 1;
  let sampleCache = {};
  let beatLength = zzfxR / BPM * 60 >> 2;

  // for each channel in order until there are no more
  for (; hasMore; channelIndex++) {

    // reset current values
    sampleBuffer = [hasMore = notFirstBeat = outSampleOffset = 0];

    // for each pattern in sequence
    sequence.forEach((patternIndex, sequenceIndex) => {
      // get pattern for current channel, use empty 1 note pattern if none found
      patternChannel = patterns[patternIndex][channelIndex] || [0, 0, 0];

      // check if there are more channels
      hasMore |= patterns[patternIndex][channelIndex]&&1;

      // get next offset, use the length of first channel
      nextSampleOffset = outSampleOffset + (patterns[patternIndex][0].length - 2 - (notFirstBeat?0:1)) * beatLength;
      // for each beat in pattern, plus one extra if end of sequence
      isSequenceEnd = sequenceIndex == sequence.length - 1;
      for (i = 2, k = outSampleOffset; i < patternChannel.length + isSequenceEnd; notFirstBeat = ++i) {

        // <channel-note>
        note = patternChannel[i];

        // stop if end, different instrument or new note
        stop = i == patternChannel.length + isSequenceEnd - 1 && isSequenceEnd ||
            instrument != (patternChannel[0] || 0) || note | 0;

        // fill buffer with samples for previous beat, most cpu intensive part
        for (j = 0; j < beatLength && notFirstBeat;

            // fade off attenuation at end of beat if stopping note, prevents clicking
            j++ > beatLength - 99 && stop && attenuation < 1? attenuation += 1 / 99 : 0
        ) {
          // copy sample to stereo buffers with panning
          sample = (1 - attenuation) * sampleBuffer[sampleOffset++] / 2 || 0;
          leftChannelBuffer[k] = (leftChannelBuffer[k] || 0) - sample * panning + sample;
          rightChannelBuffer[k] = (rightChannelBuffer[k++] || 0) + sample * panning + sample;
        }

        // set up for next note
        if (note) {
          // set attenuation
          attenuation = note % 1;
          panning = patternChannel[1] || 0;
          if (note |= 0) {
            // get cached sample
            sampleBuffer = sampleCache[
              [
                instrument = patternChannel[sampleOffset = 0] || 0,
                note
              ]
            ] = sampleCache[[instrument, note]] || (
                // add sample to cache
                instrumentParameters = [...instruments[instrument]],
                instrumentParameters[2] *= 2 ** ((note - 12) / 12),

                // allow negative values to stop notes
                note > 0 ? zzfxG(...instrumentParameters) : []
            );
          }
        }
      }

      // update the sample offset
      outSampleOffset = nextSampleOffset;
    });
  }

  return [leftChannelBuffer, rightChannelBuffer];
}
/** 
 * LittleJS Tile Layer System
 * - Caches arrays of tiles to off screen canvas for fast rendering
 * - Unlimited numbers of layers, allocates canvases as needed
 * - Interfaces with EngineObject for collision
 * - Collision layer is separate from visible layers
 * - It is recommended to have a visible layer that matches the collision
 * - Tile layers can be drawn to using their context with canvas2d
 * - Drawn directly to the main canvas without using WebGL
 * @namespace TileCollision
 */



/** The tile collision layer array, use setTileCollisionData and getTileCollisionData to access
 *  @type {Array} 
 *  @memberof TileCollision */
let tileCollision = [];

/** Size of the tile collision layer
 *  @type {Vector2} 
 *  @memberof TileCollision */
let tileCollisionSize = vec2();

/** Clear and initialize tile collision
 *  @param {Vector2} size
 *  @memberof TileCollision */
function initTileCollision(size)
{
    tileCollisionSize = size;
    tileCollision = [];
    for (let i=tileCollision.length = tileCollisionSize.area(); i--;)
        tileCollision[i] = 0;
}

/** Set tile collision data
 *  @param {Vector2} pos
 *  @param {Number}  [data]
 *  @memberof TileCollision */
function setTileCollisionData(pos, data=0)
{
    pos.arrayCheck(tileCollisionSize) && (tileCollision[(pos.y|0)*tileCollisionSize.x+pos.x|0] = data);
}

/** Get tile collision data
 *  @param {Vector2} pos
 *  @return {Number}
 *  @memberof TileCollision */
function getTileCollisionData(pos)
{
    return pos.arrayCheck(tileCollisionSize) ? tileCollision[(pos.y|0)*tileCollisionSize.x+pos.x|0] : 0;
}

/** Check if collision with another object should occur
 *  @param {Vector2}      pos
 *  @param {Vector2}      [size=(0,0)]
 *  @param {EngineObject} [object]
 *  @return {Boolean}
 *  @memberof TileCollision */
function tileCollisionTest(pos, size=vec2(), object)
{
    const minX = max(pos.x - size.x/2|0, 0);
    const minY = max(pos.y - size.y/2|0, 0);
    const maxX = min(pos.x + size.x/2, tileCollisionSize.x);
    const maxY = min(pos.y + size.y/2, tileCollisionSize.y);
    for (let y = minY; y < maxY; ++y)
    for (let x = minX; x < maxX; ++x)
    {
        const tileData = tileCollision[y*tileCollisionSize.x+x];
        if (tileData && (!object || object.collideWithTile(tileData, vec2(x, y))))
            return true;
    }
}

/** Return the center of first tile hit (does not return the exact intersection)
 *  @param {Vector2}      posStart
 *  @param {Vector2}      posEnd
 *  @param {EngineObject} [object]
 *  @return {Vector2}
 *  @memberof TileCollision */
function tileCollisionRaycast(posStart, posEnd, object)
{
    // test if a ray collides with tiles from start to end
    // todo: a way to get the exact hit point, it must still be inside the hit tile
    const delta = posEnd.subtract(posStart);
    const totalLength = delta.length();
    const normalizedDelta = delta.normalize();
    const unit = vec2(abs(1/normalizedDelta.x), abs(1/normalizedDelta.y));
    const flooredPosStart = posStart.floor();

    // setup iteration variables
    let pos = flooredPosStart;
    let xi = unit.x * (delta.x < 0 ? posStart.x - pos.x : pos.x - posStart.x + 1);
    let yi = unit.y * (delta.y < 0 ? posStart.y - pos.y : pos.y - posStart.y + 1);

    while (1)
    {
        // check for tile collision
        const tileData = getTileCollisionData(pos);
        if (tileData && (!object || object.collideWithTile(tileData, pos)))
        {
            debugRaycast && debugLine(posStart, posEnd, '#f00', .02);
            debugRaycast && debugPoint(pos.add(vec2(.5)), '#ff0');
            return pos.add(vec2(.5));
        }

        // check if past the end
        if (xi > totalLength && yi > totalLength)
            break;

        // get coordinates of the next tile to check
        if (xi > yi)
            pos.y += sign(delta.y), yi += unit.y;
        else
            pos.x += sign(delta.x), xi += unit.x;
    }

    debugRaycast && debugLine(posStart, posEnd, '#00f', .02);
}

///////////////////////////////////////////////////////////////////////////////
// Tile Layer Rendering System

/**
 * Tile layer data object stores info about how to render a tile
 * @example
 * // create tile layer data with tile index 0 and random orientation and color
 * const tileIndex = 0;
 * const direction = randInt(4)
 * const mirror = randInt(2);
 * const color = randColor();
 * const data = new TileLayerData(tileIndex, direction, mirror, color);
 */
class TileLayerData
{
    /** Create a tile layer data object, one for each tile in a TileLayer
     *  @param {Number}  [tile]      - The tile to use, untextured if undefined
     *  @param {Number}  [direction] - Integer direction of tile, in 90 degree increments
     *  @param {Boolean} [mirror]    - If the tile should be mirrored along the x axis
     *  @param {Color}   [color]     - Color of the tile */
    constructor(tile, direction=0, mirror=false, color=new Color)
    {
        /** @property {Number}  - The tile to use, untextured if undefined */
        this.tile      = tile;
        /** @property {Number}  - Integer direction of tile, in 90 degree increments */
        this.direction = direction;
        /** @property {Boolean} - If the tile should be mirrored along the x axis */
        this.mirror    = mirror;
        /** @property {Color}   - Color of the tile */
        this.color     = color;
    }

    /** Set this tile to clear, it will not be rendered */
    clear() { this.tile = this.direction = 0; this.mirror = false; this.color = new Color; }
}

/**
 * Tile Layer - cached rendering system for tile layers
 * - Each Tile layer is rendered to an off screen canvas
 * - To allow dynamic modifications, layers are rendered using canvas 2d
 * - Some devices like mobile phones are limited to 4k texture resolution
 * - So with 16x16 tiles this limits layers to 256x256 on mobile devices
 * @extends EngineObject
 * @example
 * // create tile collision and visible tile layer
 * initTileCollision(vec2(200,100));
 * const tileLayer = new TileLayer();
 */
class TileLayer extends EngineObject
{
    /** Create a tile layer object
    *  @param {Vector2}  [position=(0,0)]     - World space position
    *  @param {Vector2}  [size=tileCollisionSize] - World space size
    *  @param {TileInfo} [tileInfo]    - Tile info for layer
    *  @param {Vector2}  [scale=(1,1)] - How much to scale this layer when rendered
    *  @param {Number}   [renderOrder] - Objects are sorted by renderOrder
    */
    constructor(position, size=tileCollisionSize, tileInfo=tile(), scale=vec2(1), renderOrder=0)
    {
        super(position, size, tileInfo, 0, undefined, renderOrder);

        /** @property {HTMLCanvasElement} - The canvas used by this tile layer */
        this.canvas = document.createElement('canvas');
        /** @property {CanvasRenderingContext2D|OffscreenCanvasRenderingContext2D} - The 2D canvas context used by this tile layer */
        this.context = this.canvas.getContext('2d');
        /** @property {Vector2} - How much to scale this layer when rendered */
        this.scale = scale;
        /** @property {Boolean} - If true this layer will render to overlay canvas and appear above all objects */
        this.isOverlay = false;

        // init tile data
        this.data = [];
        for (let j = this.size.area(); j--;)
            this.data.push(new TileLayerData);

        if (headlessMode)
        {
            // disable rendering
            this.redraw       = () => {};
            this.render       = () => {};
            this.redrawStart  = () => {};
            this.redrawEnd    = () => {};
            this.drawTileData = () => {};
            this.drawCanvas2D = () => {};
        }
    }
    
    /** Set data at a given position in the array 
     *  @param {Vector2}       layerPos - Local position in array
     *  @param {TileLayerData} data     - Data to set
     *  @param {Boolean}       [redraw] - Force the tile to redraw if true */
    setData(layerPos, data, redraw=false)
    {
        if (layerPos.arrayCheck(this.size))
        {
            this.data[(layerPos.y|0)*this.size.x+layerPos.x|0] = data;
            redraw && this.drawTileData(layerPos);
        }
    }
    
    /** Get data at a given position in the array 
     *  @param {Vector2} layerPos - Local position in array
     *  @return {TileLayerData} */
    getData(layerPos)
    { return layerPos.arrayCheck(this.size) && this.data[(layerPos.y|0)*this.size.x+layerPos.x|0]; }
    
    // Tile layers are not updated
    update() {}

    // Render the tile layer, called automatically by the engine
    render()
    {
        ASSERT(mainContext != this.context, 'must call redrawEnd() after drawing tiles');

        // flush and copy gl canvas because tile canvas does not use webgl
        !glOverlay && !this.isOverlay && glCopyToContext(mainContext);
        
        // draw the entire cached level onto the canvas
        const pos = worldToScreen(this.pos.add(vec2(0,this.size.y*this.scale.y)));
        (this.isOverlay ? overlayContext : mainContext).drawImage
        (
            this.canvas, pos.x, pos.y,
            cameraScale*this.size.x*this.scale.x, cameraScale*this.size.y*this.scale.y
        );
    }

    /** Draw all the tile data to an offscreen canvas 
     *  - This may be slow in some browsers but only needs to be done once */
    redraw()
    {
        this.redrawStart(true);
        for (let x = this.size.x; x--;)
        for (let y = this.size.y; y--;)
            this.drawTileData(vec2(x,y), false);
        this.redrawEnd();
    }

    /** Call to start the redraw process
     *  - This can be used to manually update small parts of the level
     *  @param {Boolean} [clear] - Should it clear the canvas before drawing */
    redrawStart(clear=false)
    {
        // save current render settings
        /** @type {[HTMLCanvasElement, CanvasRenderingContext2D, Vector2, Vector2, number]} */
        this.savedRenderSettings = [mainCanvas, mainContext, mainCanvasSize, cameraPos, cameraScale];

        // use webgl rendering system to render the tiles if enabled
        // this works by temporally taking control of the rendering system
        mainCanvas = this.canvas;
        mainContext = this.context;
        mainCanvasSize = this.size.multiply(this.tileInfo.size);
        cameraPos = this.size.scale(.5);
        cameraScale = this.tileInfo.size.x;

        if (clear)
        {
            // clear and set size
            mainCanvas.width  = mainCanvasSize.x;
            mainCanvas.height = mainCanvasSize.y;
        }

        // disable smoothing for pixel art
        this.context.imageSmoothingEnabled = !canvasPixelated;

        // setup gl rendering if enabled
        glPreRender();
    }

    /** Call to end the redraw process */
    redrawEnd()
    {
        ASSERT(mainContext == this.context, 'must call redrawStart() before drawing tiles');
        glCopyToContext(mainContext, true);
        //debugSaveCanvas(this.canvas);

        // set stuff back to normal
        [mainCanvas, mainContext, mainCanvasSize, cameraPos, cameraScale] = this.savedRenderSettings;
    }

    /** Draw the tile at a given position in the tile grid
     *  This can be used to clear out tiles when they are destroyed
     *  Tiles can also be redrawn if isinde a redrawStart/End block
     *  @param {Vector2} layerPos 
     *  @param {Boolean} [clear] - should the old tile be cleared out
     */
    drawTileData(layerPos, clear=true)
    {
        // clear out where the tile was, for full opaque tiles this can be skipped
        const s = this.tileInfo.size;
        if (clear)
        {
            const pos = layerPos.multiply(s);
            this.context.clearRect(pos.x, this.canvas.height-pos.y, s.x, -s.y);
        }

        // draw the tile if not undefined
        const d = this.getData(layerPos);
        if (d.tile != undefined)
        {
            const pos = this.pos.add(layerPos).add(vec2(.5));
            ASSERT(mainContext == this.context, 'must call redrawStart() before drawing tiles');
            const tileInfo = tile(d.tile, s, this.tileInfo.textureIndex);
            drawTile(pos, vec2(1), tileInfo, d.color, d.direction*PI/2, d.mirror);
        }
    }

    /** Draw directly to the 2D canvas in world space (bipass webgl)
     *  @param {Vector2}  pos
     *  @param {Vector2}  size
     *  @param {Number}   angle
     *  @param {Boolean}  mirror
     *  @param {Function} drawFunction */
    drawCanvas2D(pos, size, angle, mirror, drawFunction)
    {
        const context = this.context;
        context.save();
        pos = pos.subtract(this.pos).multiply(this.tileInfo.size);
        size = size.multiply(this.tileInfo.size);
        context.translate(pos.x, this.canvas.height - pos.y);
        context.rotate(angle);
        context.scale(mirror ? -size.x : size.x, size.y);
        drawFunction(context);
        context.restore();
    }

    /** Draw a tile directly onto the layer canvas in world space
     *  @param {Vector2}  pos
     *  @param {Vector2}  [size=(1,1)]
     *  @param {TileInfo} [tileInfo]
     *  @param {Color}    [color=(1,1,1,1)]
     *  @param {Number}   [angle=0]
     *  @param {Boolean}  [mirror=0] */
    drawTile(pos, size=vec2(1), tileInfo, color=new Color, angle, mirror)
    {
        this.drawCanvas2D(pos, size, angle, mirror, (context)=>
        {
            const textureInfo = tileInfo && tileInfo.getTextureInfo();
            if (textureInfo)
            {
                context.globalAlpha = color.a; // only alpha is supported
                context.drawImage(textureInfo.image, 
                    tileInfo.pos.x,  tileInfo.pos.y, 
                    tileInfo.size.x, tileInfo.size.y, -.5, -.5, 1, 1);
                context.globalAlpha = 1;
            }
            else
            {
                // untextured
                context.fillStyle = color;
                context.fillRect(-.5, -.5, 1, 1);
            }
        });
    }

    /** Draw a rectangle directly onto the layer canvas in world space
     *  @param {Vector2} pos
     *  @param {Vector2} [size=(1,1)]
     *  @param {Color}   [color=(1,1,1,1)]
     *  @param {Number}  [angle=0] */
    drawRect(pos, size, color, angle) 
    { this.drawTile(pos, size, undefined, color, angle); }
}
/** 
 * LittleJS Particle System
 */



/**
 * Particle Emitter - Spawns particles with the given settings
 * @extends EngineObject
 * @example
 * // create a particle emitter
 * let pos = vec2(2,3);
 * let particleEmitter = new ParticleEmitter
 * (
 *     pos, 0, 1, 0, 500, PI,      // pos, angle, emitSize, emitTime, emitRate, emiteCone
 *     tile(0, 16),                // tileInfo
 *     rgb(1,1,1),   rgb(0,0,0),   // colorStartA, colorStartB
 *     rgb(1,1,1,0), rgb(0,0,0,0), // colorEndA, colorEndB
 *     2, .2, .2, .1, .05,  // particleTime, sizeStart, sizeEnd, particleSpeed, particleAngleSpeed
 *     .99, 1, 1, PI, .05,  // damping, angleDamping, gravityScale, particleCone, fadeRate, 
 *     .5, 1                // randomness, collide, additive, randomColorLinear, renderOrder
 * );
 */
class ParticleEmitter extends EngineObject
{
    /** Create a particle system with the given settings
     *  @param {Vector2} position - World space position of the emitter
     *  @param {Number} [angle] - Angle to emit the particles
     *  @param {Number|Vector2}  [emitSize] - World space size of the emitter (float for circle diameter, vec2 for rect)
     *  @param {Number} [emitTime] - How long to stay alive (0 is forever)
     *  @param {Number} [emitRate] - How many particles per second to spawn, does not emit if 0
     *  @param {Number} [emitConeAngle=PI] - Local angle to apply velocity to particles from emitter
     *  @param {TileInfo} [tileInfo] - Tile info to render particles (undefined is untextured)
     *  @param {Color} [colorStartA=(1,1,1,1)] - Color at start of life 1, randomized between start colors
     *  @param {Color} [colorStartB=(1,1,1,1)] - Color at start of life 2, randomized between start colors
     *  @param {Color} [colorEndA=(1,1,1,0)] - Color at end of life 1, randomized between end colors
     *  @param {Color} [colorEndB=(1,1,1,0)] - Color at end of life 2, randomized between end colors
     *  @param {Number} [particleTime]      - How long particles live
     *  @param {Number} [sizeStart]         - How big are particles at start
     *  @param {Number} [sizeEnd]           - How big are particles at end
     *  @param {Number} [speed]             - How fast are particles when spawned
     *  @param {Number} [angleSpeed]        - How fast are particles rotating
     *  @param {Number} [damping]           - How much to dampen particle speed
     *  @param {Number} [angleDamping]      - How much to dampen particle angular speed
     *  @param {Number} [gravityScale]      - How much gravity effect particles
     *  @param {Number} [particleConeAngle] - Cone for start particle angle
     *  @param {Number} [fadeRate]          - How quick to fade particles at start/end in percent of life
     *  @param {Number} [randomness]    - Apply extra randomness percent
     *  @param {Boolean} [collideTiles] - Do particles collide against tiles
     *  @param {Boolean} [additive]     - Should particles use addtive blend
     *  @param {Boolean} [randomColorLinear] - Should color be randomized linearly or across each component
     *  @param {Number} [renderOrder] - Render order for particles (additive is above other stuff by default)
     *  @param {Boolean}  [localSpace] - Should it be in local space of emitter (world space is default)
     */
    constructor
    ( 
        position,
        angle,
        emitSize = 0,
        emitTime = 0,
        emitRate = 100,
        emitConeAngle = PI,
        tileInfo,
        colorStartA = new Color,
        colorStartB = new Color,
        colorEndA = new Color(1,1,1,0),
        colorEndB = new Color(1,1,1,0),
        particleTime = .5,
        sizeStart = .1,
        sizeEnd = 1,
        speed = .1,
        angleSpeed = .05,
        damping = 1,
        angleDamping = 1,
        gravityScale = 0,
        particleConeAngle = PI,
        fadeRate = .1,
        randomness = .2, 
        collideTiles = false,
        additive = false,
        randomColorLinear = true,
        renderOrder = additive ? 1e9 : 0,
        localSpace = false
    )
    {
        super(position, vec2(), tileInfo, angle, undefined, renderOrder);

        // emitter settings
        /** @property {Number|Vector2} - World space size of the emitter (float for circle diameter, vec2 for rect) */
        this.emitSize = emitSize
        /** @property {Number} - How long to stay alive (0 is forever) */
        this.emitTime = emitTime;
        /** @property {Number} - How many particles per second to spawn, does not emit if 0 */
        this.emitRate = emitRate;
        /** @property {Number} - Local angle to apply velocity to particles from emitter */
        this.emitConeAngle = emitConeAngle;

        // color settings
        /** @property {Color} - Color at start of life 1, randomized between start colors */
        this.colorStartA = colorStartA;
        /** @property {Color} - Color at start of life 2, randomized between start colors */
        this.colorStartB = colorStartB;
        /** @property {Color} - Color at end of life 1, randomized between end colors */
        this.colorEndA   = colorEndA;
        /** @property {Color} - Color at end of life 2, randomized between end colors */
        this.colorEndB   = colorEndB;
        /** @property {Boolean} - Should color be randomized linearly or across each component */
        this.randomColorLinear = randomColorLinear;

        // particle settings
        /** @property {Number} - How long particles live */
        this.particleTime      = particleTime;
        /** @property {Number} - How big are particles at start */
        this.sizeStart         = sizeStart;
        /** @property {Number} - How big are particles at end */
        this.sizeEnd           = sizeEnd;
        /** @property {Number} - How fast are particles when spawned */
        this.speed             = speed;
        /** @property {Number} - How fast are particles rotating */
        this.angleSpeed        = angleSpeed;
        /** @property {Number} - How much to dampen particle speed */
        this.damping           = damping;
        /** @property {Number} - How much to dampen particle angular speed */
        this.angleDamping      = angleDamping;
        /** @property {Number} - How much does gravity effect particles */
        this.gravityScale      = gravityScale;
        /** @property {Number} - Cone for start particle angle */
        this.particleConeAngle = particleConeAngle;
        /** @property {Number} - How quick to fade in particles at start/end in percent of life */
        this.fadeRate          = fadeRate;
        /** @property {Number} - Apply extra randomness percent */
        this.randomness        = randomness;
        /** @property {Boolean} - Do particles collide against tiles */
        this.collideTiles      = collideTiles;
        /** @property {Boolean} - Should particles use addtive blend */
        this.additive          = additive;
        /** @property {Boolean} - Should it be in local space of emitter */
        this.localSpace        = localSpace;
        /** @property {Number} - If non zero the partile is drawn as a trail, stretched in the drection of velocity */
        this.trailScale        = 0;
        /** @property {Function}   - Callback when particle is destroyed */
        this.particleDestroyCallback = undefined;
        /** @property {Function}   - Callback when particle is created */
        this.particleCreateCallback = undefined;
        /** @property {Number} - Track particle emit time */
        this.emitTimeBuffer    = 0;
    }
    
    /** Update the emitter to spawn particles, called automatically by engine once each frame */
    update()
    {
        // only do default update to apply parent transforms
        this.parent && super.update();

        // update emitter
        if (!this.emitTime || this.getAliveTime() <= this.emitTime)
        {
            // emit particles
            if (this.emitRate * particleEmitRateScale)
            {
                const rate = 1/this.emitRate/particleEmitRateScale;
                for (this.emitTimeBuffer += timeDelta; this.emitTimeBuffer > 0; this.emitTimeBuffer -= rate)
                    this.emitParticle();
            }
        }
        else
            this.destroy();

        debugParticles && debugRect(this.pos, vec2(this.emitSize), '#0f0', 0, this.angle);
    }

    /** Spawn one particle
     *  @return {Particle} */
    emitParticle()
    {
        // spawn a particle
        let pos = typeof this.emitSize === 'number' ? // check if number was used
            randInCircle(this.emitSize/2)              // circle emitter
            : vec2(rand(-.5,.5), rand(-.5,.5))         // box emitter
                .multiply(this.emitSize).rotate(this.angle)
        let angle = rand(this.particleConeAngle, -this.particleConeAngle);
        if (!this.localSpace)
        {
            pos = this.pos.add(pos);
            angle += this.angle;
        }

        // randomness scales each paremeter by a percentage
        const randomness = this.randomness;
        const randomizeScale = (v)=> v + v*rand(randomness, -randomness);

        // randomize particle settings
        const particleTime  = randomizeScale(this.particleTime);
        const sizeStart     = randomizeScale(this.sizeStart);
        const sizeEnd       = randomizeScale(this.sizeEnd);
        const speed         = randomizeScale(this.speed);
        const angleSpeed    = randomizeScale(this.angleSpeed) * randSign();
        const coneAngle     = rand(this.emitConeAngle, -this.emitConeAngle);
        const colorStart    = randColor(this.colorStartA, this.colorStartB, this.randomColorLinear);
        const colorEnd      = randColor(this.colorEndA,   this.colorEndB, this.randomColorLinear);
        const velocityAngle = this.localSpace ? coneAngle : this.angle + coneAngle;
        
        // build particle
        const particle = new Particle(pos, this.tileInfo, angle, colorStart, colorEnd, particleTime, sizeStart, sizeEnd, this.fadeRate, this.additive,  this.trailScale, this.localSpace && this, this.particleDestroyCallback);
        particle.velocity      = vec2().setAngle(velocityAngle, speed);
        particle.angleVelocity = angleSpeed;
        particle.fadeRate      = this.fadeRate;
        particle.damping       = this.damping;
        particle.angleDamping  = this.angleDamping;
        particle.elasticity    = this.elasticity;
        particle.friction      = this.friction;
        particle.gravityScale  = this.gravityScale;
        particle.collideTiles  = this.collideTiles;
        particle.renderOrder   = this.renderOrder;
        particle.mirror        = !!randInt(2);

        // call particle create callaback
        this.particleCreateCallback && this.particleCreateCallback(particle);

        // return the newly created particle
        return particle;
    }

    // Particle emitters are not rendered, only the particles are
    render() {}
}

///////////////////////////////////////////////////////////////////////////////
/**
 * Particle Object - Created automatically by Particle Emitters
 * @extends EngineObject
 */
class Particle extends EngineObject
{
    /**
     * Create a particle with the passed in settings
     * Typically this is created automatically by a ParticleEmitter
     * @param {Vector2}  position   - World space position of the particle
     * @param {TileInfo} tileInfo   - Tile info to render particles
     * @param {Number}   angle      - Angle to rotate the particle
     * @param {Color}    colorStart - Color at start of life
     * @param {Color}    colorEnd   - Color at end of life
     * @param {Number}   lifeTime   - How long to live for
     * @param {Number}   sizeStart  - Size at start of life
     * @param {Number}   sizeEnd    - Size at end of life
     * @param {Number}   fadeRate   - How quick to fade in/out
     * @param {Boolean}  additive   - Does it use additive blend mode
     * @param {Number}   trailScale - If a trail, how long to make it
     * @param {ParticleEmitter} [localSpaceEmitter] - Parent emitter if local space
     * @param {Function} [destroyCallback] - Callback when particle dies
     */
    constructor(position, tileInfo, angle, colorStart, colorEnd, lifeTime, sizeStart, sizeEnd, fadeRate, additive, trailScale, localSpaceEmitter, destroyCallback
    )
    { 
        super(position, vec2(), tileInfo, angle); 
    
        /** @property {Color} - Color at start of life */
        this.colorStart = colorStart;
        /** @property {Color} - Calculated change in color */
        this.colorEndDelta = colorEnd.subtract(colorStart);
        /** @property {Number} - How long to live for */
        this.lifeTime = lifeTime;
        /** @property {Number} - Size at start of life */
        this.sizeStart = sizeStart;
        /** @property {Number} - Calculated change in size */
        this.sizeEndDelta = sizeEnd - sizeStart;
        /** @property {Number} - How quick to fade in/out */
        this.fadeRate = fadeRate;
        /** @property {Boolean} - Is it additive */
        this.additive = additive;
        /** @property {Number} - If a trail, how long to make it */
        this.trailScale = trailScale;
        /** @property {ParticleEmitter} - Parent emitter if local space */
        this.localSpaceEmitter = localSpaceEmitter;
        /** @property {Function} - Called when particle dies */
        this.destroyCallback = destroyCallback;

        // particles use circular clamped speed
        this.clampSpeedLinear = false;
    }

    /** Render the particle, automatically called each frame, sorted by renderOrder */
    render()
    {
        // modulate size and color
        const p = min((time - this.spawnTime) / this.lifeTime, 1);
        const radius = this.sizeStart + p * this.sizeEndDelta;
        const size = vec2(radius);
        const fadeRate = this.fadeRate/2;
        const color = new Color(
            this.colorStart.r + p * this.colorEndDelta.r,
            this.colorStart.g + p * this.colorEndDelta.g,
            this.colorStart.b + p * this.colorEndDelta.b,
            (this.colorStart.a + p * this.colorEndDelta.a) * 
             (p < fadeRate ? p/fadeRate : p > 1-fadeRate ? (1-p)/fadeRate : 1)); // fade alpha

        // draw the particle
        this.additive && setBlendMode(true);

        let pos = this.pos, angle = this.angle;
        if (this.localSpaceEmitter)
        {
            // in local space of emitter
            pos = this.localSpaceEmitter.pos.add(pos.rotate(-this.localSpaceEmitter.angle)); 
            angle += this.localSpaceEmitter.angle;
        }
        if (this.trailScale)
        {
            // trail style particles
            let velocity = this.velocity;
            if (this.localSpaceEmitter)
                velocity = velocity.rotate(-this.localSpaceEmitter.angle);
            const speed = velocity.length();
            if (speed)
            {
                const direction = velocity.scale(1/speed);
                const trailLength = speed * this.trailScale;
                size.y = max(size.x, trailLength);
                angle = direction.angle();
                drawTile(pos.add(direction.multiply(vec2(0,-trailLength/2))), size, this.tileInfo, color, angle, this.mirror);
            }
        }
        else
            drawTile(pos, size, this.tileInfo, color, angle, this.mirror);
        this.additive && setBlendMode();
        debugParticles && debugRect(pos, size, '#f005', 0, angle);

        if (p == 1)
        {
            // destroy particle when it's time runs out
            this.color = color;
            this.size = size;
            this.destroyCallback && this.destroyCallback(this);
            this.destroyed = 1;
        }
    }
}
/** 
 * LittleJS Medal System
 * - Tracks and displays medals
 * - Saves medals to local storage
 * - Newgrounds integration
 * @namespace Medals
 */



/** List of all medals
 *  @type {Object}
 *  @memberof Medals */
const medals = {};

// Engine internal variables not exposed to documentation
let medalsDisplayQueue = [], medalsSaveName, medalsDisplayTimeLast;

///////////////////////////////////////////////////////////////////////////////

/** Initialize medals with a save name used for storage
 *  - Call this after creating all medals
 *  - Checks if medals are unlocked
 *  @param {String} saveName
 *  @memberof Medals */
function medalsInit(saveName)
{
    // check if medals are unlocked
    medalsSaveName = saveName;
    if (!debugMedals)
        medalsForEach(medal=> medal.unlocked = (localStorage[medal.storageKey()] | 0));

    // engine automatically renders medals
    engineAddPlugin(undefined, medalsRender);
    function medalsRender()
    {
        if (!medalsDisplayQueue.length)
            return;
        
        // update first medal in queue
        const medal = medalsDisplayQueue[0];
        const time = timeReal - medalsDisplayTimeLast;
        if (!medalsDisplayTimeLast)
            medalsDisplayTimeLast = timeReal;
        else if (time > medalDisplayTime)
        {
            medalsDisplayTimeLast = 0;
            medalsDisplayQueue.shift();
        }
        else
        {
            // slide on/off medals
            const slideOffTime = medalDisplayTime - medalDisplaySlideTime;
            const hidePercent = 
                time < medalDisplaySlideTime ? 1 - time / medalDisplaySlideTime :
                time > slideOffTime ? (time - slideOffTime) / medalDisplaySlideTime : 0;
            medal.render(hidePercent);
        }
    }
}

/** Calls a function for each medal
 *  @param {Function} callback
 *  @memberof Medals */
function medalsForEach(callback)
{ Object.values(medals).forEach(medal=>callback(medal)); }

///////////////////////////////////////////////////////////////////////////////

/** 
 * Medal - Tracks an unlockable medal 
 * @example
 * // create a medal
 * const medal_example = new Medal(0, 'Example Medal', 'More info about the medal goes here.', '🎖️');
 * 
 * // initialize medals
 * medalsInit('Example Game');
 * 
 * // unlock the medal
 * medal_example.unlock();
 */
class Medal
{
    /** Create a medal object and adds it to the list of medals
     *  @param {Number} id            - The unique identifier of the medal
     *  @param {String} name          - Name of the medal
     *  @param {String} [description] - Description of the medal
     *  @param {String} [icon]        - Icon for the medal
     *  @param {String} [src]         - Image location for the medal
     */
    constructor(id, name, description='', icon='🏆', src)
    {
        ASSERT(id >= 0 && !medals[id]);

        // save attributes and add to list of medals
        medals[this.id = id] = this;
        this.name = name;
        this.description = description;
        this.icon = icon;
        if (src)
            (this.image = new Image).src = src;
    }

    /** Unlocks a medal if not already unlocked */
    unlock()
    {
        if (medalsPreventUnlock || this.unlocked)
            return;

        // save the medal
        ASSERT(medalsSaveName, 'save name must be set');
        localStorage[this.storageKey()] = this.unlocked = 1;
        medalsDisplayQueue.push(this);
    }

    /** Render a medal
     *  @param {Number} [hidePercent] - How much to slide the medal off screen
     */
    render(hidePercent=0)
    {
        const context = overlayContext;
        const width = min(medalDisplaySize.x, mainCanvas.width);
        const x = overlayCanvas.width - width;
        const y = -medalDisplaySize.y*hidePercent;

        // draw containing rect and clip to that region
        context.save();
        context.beginPath();
        context.fillStyle = new Color(.9,.9,.9).toString();
        context.strokeStyle = new Color(0,0,0).toString();
        context.lineWidth = 3;
        context.rect(x, y, width, medalDisplaySize.y);
        context.fill();
        context.stroke();
        context.clip();

        // draw the icon and text
        this.renderIcon(vec2(x+15+medalDisplayIconSize/2, y+medalDisplaySize.y/2));
        const pos = vec2(x+medalDisplayIconSize+30, y+28);
        drawTextScreen(this.name, pos, 38, new Color(0,0,0), 0, undefined, 'left');
        pos.y += 32;
        drawTextScreen(this.description, pos, 24, new Color(0,0,0), 0, undefined, 'left');
        context.restore();
    }

    /** Render the icon for a medal
     *  @param {Vector2} pos - Screen space position
     *  @param {Number} [size=medalDisplayIconSize] - Screen space size
     */
    renderIcon(pos, size=medalDisplayIconSize)
    {
        // draw the image or icon
        if (this.image)
            overlayContext.drawImage(this.image, pos.x-size/2, pos.y-size/2, size, size);
        else
            drawTextScreen(this.icon, pos, size*.7, new Color(0,0,0));
    }
 
    // Get local storage key used by the medal
    storageKey() { return medalsSaveName + '_' + this.id; }
}
/**
 * LittleJS WebGL Interface
 * - All webgl used by the engine is wrapped up here
 * - For normal stuff you won't need to see or call anything in this file
 * - For advanced stuff there are helper functions to create shaders, textures, etc
 * - Can be disabled with glEnable to revert to 2D canvas rendering
 * - Batches sprite rendering on GPU for incredibly fast performance
 * - Sprite transform math is done in the shader where possible
 * - Supports shadertoy style post processing shaders
 * @namespace WebGL
 */



/** The WebGL canvas which appears above the main canvas and below the overlay canvas
 *  @type {HTMLCanvasElement}
 *  @memberof WebGL */
let glCanvas;

/** 2d context for glCanvas
 *  @type {WebGL2RenderingContext}
 *  @memberof WebGL */
let glContext;

// WebGL internal variables not exposed to documentation
let glShader, glActiveTexture, glArrayBuffer, glGeometryBuffer, glPositionData, glColorData, glInstanceCount, glAdditive, glBatchAdditive;

///////////////////////////////////////////////////////////////////////////////

// Initalize WebGL, called automatically by the engine
function glInit()
{
    if (!glEnable || headlessMode) return;

    // create the canvas and textures
    glCanvas = document.createElement('canvas');
    glContext = glCanvas.getContext('webgl2');

    // some browsers are much faster without copying the gl buffer so we just overlay it instead
    glOverlay && document.body.appendChild(glCanvas);

    // setup vertex and fragment shaders
    glShader = glCreateProgram(
        '#version 300 es\n' +     // specify GLSL ES version
        'precision highp float;'+ // use highp for better accuracy
        'uniform mat4 m;'+        // transform matrix
        'in vec2 g;'+             // in: geometry
        'in vec4 p,u,c,a;'+       // in: position/size, uvs, color, additiveColor
        'in float r;'+            // in: rotation
        'out vec2 v;'+            // out: uv
        'out vec4 d,e;'+          // out: color, additiveColor
        'void main(){'+           // shader entry point
        'vec2 s=(g-.5)*p.zw;'+    // get size offset
        'gl_Position=m*vec4(p.xy+s*cos(r)-vec2(-s.y,s)*sin(r),1,1);'+ // transform position
        'v=mix(u.xw,u.zy,g);'+    // pass uv to fragment shader
        'd=c;e=a;'+               // pass colors to fragment shader
        '}'                       // end of shader
        ,
        '#version 300 es\n' +     // specify GLSL ES version
        'precision highp float;'+ // use highp for better accuracy
        'uniform sampler2D s;'+   // texture
        'in vec2 v;'+             // in: uv
        'in vec4 d,e;'+           // in: color, additiveColor
        'out vec4 c;'+            // out: color
        'void main(){'+           // shader entry point
        'c=texture(s,v)*d+e;'+    // modulate texture by color plus additive
        '}'                       // end of shader
    );

    // init buffers
    const glInstanceData = new ArrayBuffer(gl_INSTANCE_BUFFER_SIZE);
    glPositionData = new Float32Array(glInstanceData);
    glColorData = new Uint32Array(glInstanceData);
    glArrayBuffer = glContext.createBuffer();
    glGeometryBuffer = glContext.createBuffer();

    // create the geometry buffer, triangle strip square
    const geometry = new Float32Array([glInstanceCount=0,0,1,0,0,1,1,1]);
    glContext.bindBuffer(gl_ARRAY_BUFFER, glGeometryBuffer);
    glContext.bufferData(gl_ARRAY_BUFFER, geometry, gl_STATIC_DRAW);
}

// Setup render each frame, called automatically by engine
function glPreRender()
{
    if (!glEnable || headlessMode) return;

    // clear and set to same size as main canvas
    glContext.viewport(0, 0, glCanvas.width=mainCanvas.width, glCanvas.height=mainCanvas.height);
    glContext.clear(gl_COLOR_BUFFER_BIT);

    // set up the shader
    glContext.useProgram(glShader);
    glContext.activeTexture(gl_TEXTURE0);
    glContext.bindTexture(gl_TEXTURE_2D, glActiveTexture = textureInfos[0].glTexture);

    // set vertex attributes
    let offset = glAdditive = glBatchAdditive = 0;
    let initVertexAttribArray = (name, type, typeSize, size)=>
    {
        const location = glContext.getAttribLocation(glShader, name);
        const stride = typeSize && gl_INSTANCE_BYTE_STRIDE; // only if not geometry
        const divisor = typeSize && 1; // only if not geometry
        const normalize = typeSize==1; // only if color
        glContext.enableVertexAttribArray(location);
        glContext.vertexAttribPointer(location, size, type, normalize, stride, offset);
        glContext.vertexAttribDivisor(location, divisor);
        offset += size*typeSize;
    }
    glContext.bindBuffer(gl_ARRAY_BUFFER, glGeometryBuffer);
    initVertexAttribArray('g', gl_FLOAT, 0, 2); // geometry
    glContext.bindBuffer(gl_ARRAY_BUFFER, glArrayBuffer);
    glContext.bufferData(gl_ARRAY_BUFFER, gl_INSTANCE_BUFFER_SIZE, gl_DYNAMIC_DRAW);
    initVertexAttribArray('p', gl_FLOAT, 4, 4); // position & size
    initVertexAttribArray('u', gl_FLOAT, 4, 4); // texture coords
    initVertexAttribArray('c', gl_UNSIGNED_BYTE, 1, 4); // color
    initVertexAttribArray('a', gl_UNSIGNED_BYTE, 1, 4); // additiveColor
    initVertexAttribArray('r', gl_FLOAT, 4, 1); // rotation

    // build the transform matrix
    const s = vec2(2*cameraScale).divide(mainCanvasSize);
    const p = vec2(-1).subtract(cameraPos.multiply(s));
    glContext.uniformMatrix4fv(glContext.getUniformLocation(glShader, 'm'), false,
        [
            s.x, 0,   0,   0,
            0,   s.y, 0,   0,
            1,   1,   1,   1,
            p.x, p.y, 0,   0
        ]
    );
}

/** Set the WebGl texture, called automatically if using multiple textures
 *  - This may also flush the gl buffer resulting in more draw calls and worse performance
 *  @param {WebGLTexture} texture
 *  @memberof WebGL */
function glSetTexture(texture)
{
    // must flush cache with the old texture to set a new one
    if (headlessMode || texture == glActiveTexture)
        return;

    glFlush();
    glContext.bindTexture(gl_TEXTURE_2D, glActiveTexture = texture);
}

/** Compile WebGL shader of the given type, will throw errors if in debug mode
 *  @param {String} source
 *  @param {Number} type
 *  @return {WebGLShader}
 *  @memberof WebGL */
function glCompileShader(source, type)
{
    // build the shader
    const shader = glContext.createShader(type);
    glContext.shaderSource(shader, source);
    glContext.compileShader(shader);

    // check for errors
    if (debug && !glContext.getShaderParameter(shader, gl_COMPILE_STATUS))
        throw glContext.getShaderInfoLog(shader);
    return shader;
}

/** Create WebGL program with given shaders
 *  @param {String} vsSource
 *  @param {String} fsSource
 *  @return {WebGLProgram}
 *  @memberof WebGL */
function glCreateProgram(vsSource, fsSource)
{
    // build the program
    const program = glContext.createProgram();
    glContext.attachShader(program, glCompileShader(vsSource, gl_VERTEX_SHADER));
    glContext.attachShader(program, glCompileShader(fsSource, gl_FRAGMENT_SHADER));
    glContext.linkProgram(program);

    // check for errors
    if (debug && !glContext.getProgramParameter(program, gl_LINK_STATUS))
        throw glContext.getProgramInfoLog(program);
    return program;
}

/** Create WebGL texture from an image and init the texture settings
 *  @param {HTMLImageElement} image
 *  @return {WebGLTexture}
 *  @memberof WebGL */
function glCreateTexture(image)
{
    // build the texture
    const texture = glContext.createTexture();
    glContext.bindTexture(gl_TEXTURE_2D, texture);
    if (image)
        glContext.texImage2D(gl_TEXTURE_2D, 0, gl_RGBA, gl_RGBA, gl_UNSIGNED_BYTE, image);

    // use point filtering for pixelated rendering
    const filter = canvasPixelated ? gl_NEAREST : gl_LINEAR;
    glContext.texParameteri(gl_TEXTURE_2D, gl_TEXTURE_MIN_FILTER, filter);
    glContext.texParameteri(gl_TEXTURE_2D, gl_TEXTURE_MAG_FILTER, filter);
    return texture;
}

/** Draw all sprites and clear out the buffer, called automatically by the system whenever necessary
 *  @memberof WebGL */
function glFlush()
{
    if (!glInstanceCount) return;

    const destBlend = glBatchAdditive ? gl_ONE : gl_ONE_MINUS_SRC_ALPHA;
    glContext.blendFuncSeparate(gl_SRC_ALPHA, destBlend, gl_ONE, destBlend);
    glContext.enable(gl_BLEND);

    // draw all the sprites in the batch and reset the buffer
    glContext.bufferSubData(gl_ARRAY_BUFFER, 0, glPositionData);
    glContext.drawArraysInstanced(gl_TRIANGLE_STRIP, 0, 4, glInstanceCount);
    if (showWatermark)
        drawCount += glInstanceCount;
    glInstanceCount = 0;
    glBatchAdditive = glAdditive;
}

/** Draw any sprites still in the buffer, copy to main canvas and clear
 *  @param {CanvasRenderingContext2D|OffscreenCanvasRenderingContext2D} context
 *  @param {Boolean} [forceDraw]
 *  @memberof WebGL */
function glCopyToContext(context, forceDraw=false)
{
    if (!glEnable || !glInstanceCount && !forceDraw) return;

    glFlush();

    // do not draw in overlay mode because the canvas is visible
    if (!glOverlay || forceDraw)
        context.drawImage(glCanvas, 0, 0);
}

/** Add a sprite to the gl draw list, used by all gl draw functions
 *  @param {Number} x
 *  @param {Number} y
 *  @param {Number} sizeX
 *  @param {Number} sizeY
 *  @param {Number} angle
 *  @param {Number} uv0X
 *  @param {Number} uv0Y
 *  @param {Number} uv1X
 *  @param {Number} uv1Y
 *  @param {Number} rgba
 *  @param {Number} [rgbaAdditive=0]
 *  @memberof WebGL */
function glDraw(x, y, sizeX, sizeY, angle, uv0X, uv0Y, uv1X, uv1Y, rgba, rgbaAdditive=0)
{
    ASSERT(typeof rgba == 'number' && typeof rgbaAdditive == 'number', 'invalid color');

    // flush if there is not enough room or if different blend mode
    if (glInstanceCount >= gl_MAX_INSTANCES || glBatchAdditive != glAdditive)
        glFlush();

    let offset = glInstanceCount * gl_INDICIES_PER_INSTANCE;
    glPositionData[offset++] = x;
    glPositionData[offset++] = y;
    glPositionData[offset++] = sizeX;
    glPositionData[offset++] = sizeY;
    glPositionData[offset++] = uv0X;
    glPositionData[offset++] = uv0Y;
    glPositionData[offset++] = uv1X;
    glPositionData[offset++] = uv1Y;
    glColorData[offset++] = rgba;
    glColorData[offset++] = rgbaAdditive;
    glPositionData[offset++] = angle;
    glInstanceCount++;
}

///////////////////////////////////////////////////////////////////////////////
// store gl constants as integers so their name doesn't use space in minifed
const
gl_ONE = 1,
gl_TRIANGLE_STRIP = 5,
gl_SRC_ALPHA = 770,
gl_ONE_MINUS_SRC_ALPHA = 771,
gl_BLEND = 3042,
gl_TEXTURE_2D = 3553,
gl_UNSIGNED_BYTE = 5121,
gl_FLOAT = 5126,
gl_RGBA = 6408,
gl_NEAREST = 9728,
gl_LINEAR = 9729,
gl_TEXTURE_MAG_FILTER = 10240,
gl_TEXTURE_MIN_FILTER = 10241,
gl_COLOR_BUFFER_BIT = 16384,
gl_TEXTURE0 = 33984,
gl_ARRAY_BUFFER = 34962,
gl_STATIC_DRAW = 35044,
gl_DYNAMIC_DRAW = 35048,
gl_FRAGMENT_SHADER = 35632,
gl_VERTEX_SHADER = 35633,
gl_COMPILE_STATUS = 35713,
gl_LINK_STATUS = 35714,
gl_UNPACK_FLIP_Y_WEBGL = 37440,

// constants for batch rendering
gl_INDICIES_PER_INSTANCE = 11,
gl_MAX_INSTANCES = 1e4,
gl_INSTANCE_BYTE_STRIDE = gl_INDICIES_PER_INSTANCE * 4, // 11 * 4
gl_INSTANCE_BUFFER_SIZE = gl_MAX_INSTANCES * gl_INSTANCE_BYTE_STRIDE;
/** 
 * LittleJS - The Tiny Fast JavaScript Game Engine
 * MIT License - Copyright 2021 Frank Force
 * 
 * Engine Features
 * - Object oriented system with base class engine object
 * - Base class object handles update, physics, collision, rendering, etc
 * - Engine helper classes and functions like Vector2, Color, and Timer
 * - Super fast rendering system for tile sheets
 * - Sound effects audio with zzfx and music with zzfxm
 * - Input processing system with gamepad and touchscreen support
 * - Tile layer rendering and collision system
 * - Particle effect system
 * - Medal system tracks and displays achievements
 * - Debug tools and debug rendering system
 * - Post processing effects
 * - Call engineInit() to start it up!
 * @namespace Engine
 */



/** Name of engine
 *  @type {String}
 *  @default
 *  @memberof Engine */
const engineName = 'LittleJS';

/** Version of engine
 *  @type {String}
 *  @default
 *  @memberof Engine */
const engineVersion = '1.9.11';

/** Frames per second to update
 *  @type {Number}
 *  @default
 *  @memberof Engine */
const frameRate = 60;

/** How many seconds each frame lasts, engine uses a fixed time step
 *  @type {Number}
 *  @default 1/60
 *  @memberof Engine */
const timeDelta = 1/frameRate;

/** Array containing all engine objects
 *  @type {Array}
 *  @memberof Engine */
let engineObjects = [];

/** Array with only objects set to collide with other objects this frame (for optimization)
 *  @type {Array}
 *  @memberof Engine */
let engineObjectsCollide = [];

/** Current update frame, used to calculate time
 *  @type {Number}
 *  @memberof Engine */
let frame = 0;

/** Current engine time since start in seconds
 *  @type {Number}
 *  @memberof Engine */
let time = 0;

/** Actual clock time since start in seconds (not affected by pause or frame rate clamping)
 *  @type {Number}
 *  @memberof Engine */
let timeReal = 0;

/** Is the game paused? Causes time and objects to not be updated
 *  @type {Boolean}
 *  @default false
 *  @memberof Engine */
let paused = false;

/** Set if game is paused
 *  @param {Boolean} isPaused
 *  @memberof Engine */
function setPaused(isPaused) { paused = isPaused; }

// Frame time tracking
let frameTimeLastMS = 0, frameTimeBufferMS = 0, averageFPS = 0;

///////////////////////////////////////////////////////////////////////////////
// plugin hooks

const pluginUpdateList = [], pluginRenderList = [];

/** Add a new update function for a plugin
 *  @param {Function} [updateFunction]
 *  @param {Function} [renderFunction]
 *  @memberof Engine */
function engineAddPlugin(updateFunction, renderFunction)
{
    updateFunction && pluginUpdateList.push(updateFunction);
    renderFunction && pluginRenderList.push(renderFunction);
}

///////////////////////////////////////////////////////////////////////////////
// Main engine functions

/** Startup LittleJS engine with your callback functions
 *  @param {Function} gameInit       - Called once after the engine starts up, setup the game
 *  @param {Function} gameUpdate     - Called every frame at 60 frames per second, handle input and update the game state
 *  @param {Function} gameUpdatePost - Called after physics and objects are updated, setup camera and prepare for render
 *  @param {Function} gameRender     - Called before objects are rendered, draw any background effects that appear behind objects
 *  @param {Function} gameRenderPost - Called after objects are rendered, draw effects or hud that appear above all objects
 *  @param {Array} [imageSources=['tiles.png']] - Image to load
 *  @memberof Engine */
function engineInit(gameInit, gameUpdate, gameUpdatePost, gameRender, gameRenderPost, imageSources=['tiles.png'])
{
    ASSERT(Array.isArray(imageSources), 'pass in images as array');

    // Called automatically by engine to setup render system
    function enginePreRender()
    {
        // save canvas size
        mainCanvasSize = vec2(mainCanvas.width, mainCanvas.height);

        // disable smoothing for pixel art
        mainContext.imageSmoothingEnabled = !canvasPixelated;

        // setup gl rendering if enabled
        glPreRender();
    }

    // internal update loop for engine
    function engineUpdate(frameTimeMS=0)
    {
        // update time keeping
        let frameTimeDeltaMS = frameTimeMS - frameTimeLastMS;
        frameTimeLastMS = frameTimeMS;
        if (debug || showWatermark)
            averageFPS = lerp(.05, averageFPS, 1e3/(frameTimeDeltaMS||1));
        const debugSpeedUp   = debug && keyIsDown('Equal'); // +
        const debugSpeedDown = debug && keyIsDown('Minus'); // -
        if (debug) // +/- to speed/slow time
            frameTimeDeltaMS *= debugSpeedUp ? 5 : debugSpeedDown ? .2 : 1;
        timeReal += frameTimeDeltaMS / 1e3;
        frameTimeBufferMS += paused ? 0 : frameTimeDeltaMS;
        if (!debugSpeedUp)
            frameTimeBufferMS = min(frameTimeBufferMS, 50); // clamp in case of slow framerate

        updateCanvas();

        if (paused)
        {
            // update object transforms even when paused
            for (const o of engineObjects)
                o.parent || o.updateTransforms();
            inputUpdate();
            debugUpdate();
            gameUpdatePost();
            inputUpdatePost();
        }
        else
        {
            // apply time delta smoothing, improves smoothness of framerate in some browsers
            let deltaSmooth = 0;
            if (frameTimeBufferMS < 0 && frameTimeBufferMS > -9)
            {
                // force at least one update each frame since it is waiting for refresh
                deltaSmooth = frameTimeBufferMS;
                frameTimeBufferMS = 0;
            }
            
            // update multiple frames if necessary in case of slow framerate
            for (;frameTimeBufferMS >= 0; frameTimeBufferMS -= 1e3 / frameRate)
            {
                // increment frame and update time
                time = frame++ / frameRate;

                // update game and objects
                inputUpdate();
                gameUpdate();
                pluginUpdateList.forEach(f=>f());
                engineObjectsUpdate();

                // do post update
                debugUpdate();
                gameUpdatePost();
                inputUpdatePost();
            }

            // add the time smoothing back in
            frameTimeBufferMS += deltaSmooth;
        }

        if (!headlessMode)
        {
            // render sort then render while removing destroyed objects
            enginePreRender();
            gameRender();
            engineObjects.sort((a,b)=> a.renderOrder - b.renderOrder);
            for (const o of engineObjects)
                o.destroyed || o.render();
            gameRenderPost();
            pluginRenderList.forEach(f=>f());
            touchGamepadRender();
            debugRender();
            glCopyToContext(mainContext);

            if (showWatermark)
            {
                // update fps
                overlayContext.textAlign = 'right';
                overlayContext.textBaseline = 'top';
                overlayContext.font = '1em monospace';
                overlayContext.fillStyle = '#000';
                const text = engineName + ' ' + 'v' + engineVersion + ' / ' 
                    + drawCount + ' / ' + engineObjects.length + ' / ' + averageFPS.toFixed(1)
                    + (glEnable ? ' GL' : ' 2D') ;
                overlayContext.fillText(text, mainCanvas.width-3, 3);
                overlayContext.fillStyle = '#fff';
                overlayContext.fillText(text, mainCanvas.width-2, 2);
                drawCount = 0;
            }
        }

        requestAnimationFrame(engineUpdate);
    }

    function updateCanvas()
    {
        if (headlessMode) return;
        
        if (canvasFixedSize.x)
        {
            // clear canvas and set fixed size
            mainCanvas.width  = canvasFixedSize.x;
            mainCanvas.height = canvasFixedSize.y;
            
            // fit to window by adding space on top or bottom if necessary
            const aspect = innerWidth / innerHeight;
            const fixedAspect = mainCanvas.width / mainCanvas.height;
            (glCanvas||mainCanvas).style.width = mainCanvas.style.width = overlayCanvas.style.width  = aspect < fixedAspect ? '100%' : '';
            (glCanvas||mainCanvas).style.height = mainCanvas.style.height = overlayCanvas.style.height = aspect < fixedAspect ? '' : '100%';
        }
        else
        {
            // clear canvas and set size to same as window
            mainCanvas.width  = min(innerWidth,  canvasMaxSize.x);
            mainCanvas.height = min(innerHeight, canvasMaxSize.y);
        }
        
        // clear overlay canvas and set size
        overlayCanvas.width  = mainCanvas.width;
        overlayCanvas.height = mainCanvas.height;

        // save canvas size
        mainCanvasSize = vec2(mainCanvas.width, mainCanvas.height);
    }

    function startEngine()
    {
        gameInit();
        engineUpdate();
    }

    if (headlessMode)
    {
        startEngine();
        return;
    }

    // setup html
    const styleBody = 
        'margin:0;overflow:hidden;' + // fill the window
        'background:#000;' +          // set background color
        'user-select:none;' +         // prevent hold to select
        '-webkit-user-select:none;' + // compatibility for ios
        (!touchInputEnable ? '' :     // no touch css setttings
        'touch-action:none;' +        // prevent mobile pinch to resize
        '-webkit-touch-callout:none');// compatibility for ios
    document.body.style.cssText = styleBody;
    document.body.appendChild(mainCanvas = document.createElement('canvas'));
    mainContext = mainCanvas.getContext('2d');

    // init stuff and start engine
    inputInit();
    audioInit();
    debugInit();
    glInit();

    // create overlay canvas for hud to appear above gl canvas
    document.body.appendChild(overlayCanvas = document.createElement('canvas'));
    overlayContext = overlayCanvas.getContext('2d');

    // set canvas style
    const styleCanvas = 'position:absolute;' +             // position
        'top:50%;left:50%;transform:translate(-50%,-50%)'; // center
    (glCanvas||mainCanvas).style.cssText = mainCanvas.style.cssText = overlayCanvas.style.cssText = styleCanvas;
    updateCanvas();
    
    // create promises for loading images
    const promises = imageSources.map((src, textureIndex)=>
        new Promise(resolve => 
        {
            const image = new Image;
            image.onerror = image.onload = ()=> 
            {
                textureInfos[textureIndex] = new TextureInfo(image);
                resolve();
            }
            image.src = src;
        })
    );

    // draw splash screen
    showSplashScreen && promises.push(new Promise(resolve => 
    {
        let t = 0;
        console.log(`${engineName} Engine v${engineVersion}`);
        updateSplash();
        function updateSplash()
        {
            clearInput();
            drawEngineSplashScreen(t+=.01);
            t>1 ? resolve() : setTimeout(updateSplash, 16);
        }
    }));

    // load all of the images
    Promise.all(promises).then(startEngine);
}

/** Update each engine object, remove destroyed objects, and update time
 *  @memberof Engine */
function engineObjectsUpdate()
{
    // get list of solid objects for physics optimzation
    engineObjectsCollide = engineObjects.filter(o=>o.collideSolidObjects);

    // recursive object update
    function updateObject(o)
    {
        if (!o.destroyed)
        {
            o.update();
            for (const child of o.children)
                updateObject(child);
        }
    }
    for (const o of engineObjects)
    {
        // update top level objects
        if (!o.parent)
        {
            updateObject(o);
            o.updateTransforms();
        }
    }

    // remove destroyed objects
    engineObjects = engineObjects.filter(o=>!o.destroyed);
}

/** Destroy and remove all objects
 *  @memberof Engine */
function engineObjectsDestroy()
{
    for (const o of engineObjects)
        o.parent || o.destroy();
    engineObjects = engineObjects.filter(o=>!o.destroyed);
}

/** Collects all object within a given area
 *  @param {Vector2} [pos]                 - Center of test area, or undefined for all objects
 *  @param {Number|Vector2} [size]         - Radius of circle if float, rectangle size if Vector2
 *  @param {Array} [objects=engineObjects] - List of objects to check
 *  @return {Array}                        - List of collected objects
 *  @memberof Engine */
function engineObjectsCollect(pos, size, objects=engineObjects)
{
    const collectedObjects = [];
    if (!pos) // all objects
    {
        for (const o of objects)
            collectedObjects.push(o);
    }
    else if (size instanceof Vector2)  // bounding box test
    {
        for (const o of objects)
            isOverlapping(pos, size, o.pos, o.size) && collectedObjects.push(o);
    }
    else  // circle test
    {
        const sizeSquared = size*size;
        for (const o of objects)
            pos.distanceSquared(o.pos) < sizeSquared && collectedObjects.push(o);
    }
    return collectedObjects;
}

/** Triggers a callback for each object within a given area
 *  @param {Vector2} [pos]                 - Center of test area, or undefined for all objects
 *  @param {Number|Vector2} [size]         - Radius of circle if float, rectangle size if Vector2
 *  @param {Function} [callbackFunction]   - Calls this function on every object that passes the test
 *  @param {Array} [objects=engineObjects] - List of objects to check
 *  @memberof Engine */
function engineObjectsCallback(pos, size, callbackFunction, objects=engineObjects)
{ engineObjectsCollect(pos, size, objects).forEach(o => callbackFunction(o)); }

/** Return a list of objects intersecting a ray
 *  @param {Vector2} start
 *  @param {Vector2} end
 *  @param {Array} [objects=engineObjects] - List of objects to check
 *  @return {Array} - List of objects hit
 *  @memberof Engine */
function engineObjectsRaycast(start, end, objects=engineObjects)
{
    const hitObjects = [];
    for (const o of objects)
    {
        if (o.collideRaycast && isIntersecting(start, end, o.pos, o.size))
        {
            debugRaycast && debugRect(o.pos, o.size, '#f00');
            hitObjects.push(o);
        }
    }

    debugRaycast && debugLine(start, end, hitObjects.length ? '#f00' : '#00f', .02);
    return hitObjects;
}

///////////////////////////////////////////////////////////////////////////////
// LittleJS splash screen and logo

function drawEngineSplashScreen(t)
{
    const x = overlayContext;
    const w = overlayCanvas.width = innerWidth;
    const h = overlayCanvas.height = innerHeight;

    {
        // background
        const p3 = percent(t, 1, .8);
        const p4 = percent(t, 0, .5);
        const g = x.createRadialGradient(w/2,h/2,0,w/2,h/2,Math.hypot(w,h)*.7);
        g.addColorStop(0,hsl(0,0,lerp(p4,0,p3/2),p3).toString());
        g.addColorStop(1,hsl(0,0,0,p3).toString());
        x.save();
        x.fillStyle = g;
        x.fillRect(0,0,w,h);
    }

    // draw LittleJS logo...
    const rect = (X, Y, W, H, C)=>
    {
        x.beginPath();
        x.rect(X,Y,W,C?H*p:H);
        x.fillStyle = C;
        C ? x.fill() : x.stroke();
    };
    const line = (X, Y, Z, W)=>
    {
        x.beginPath();
        x.lineTo(X,Y);
        x.lineTo(Z,W);
        x.stroke();
    };
    const circle = (X, Y, R, A=0, B=2*PI, C, F)=>
    {
        const D = (A+B)/2, E = p*(B-A)/2;
        x.beginPath();
        F && x.lineTo(X,Y);
        x.arc(X,Y,R,D-E,D+E);
        x.fillStyle = C;
        C ? x.fill() : x.stroke();
    };
    const color = (c=0, l=0) =>
        hsl([.98,.3,.57,.14][c%4]-10,.8,[0,.3,.5,.8,.9][l]).toString();
    const alpha = wave(1,1,t);
    const p = percent(alpha, .1, .5);

    // setup
    x.translate(w/2,h/2);
    const size = min(6, min(w,h)/99); // fit to screen
    x.scale(size,size);
    x.translate(-40,-35);
    x.lineJoin = x.lineCap = 'round';
    x.lineWidth = .1 + p*1.9;

    // drawing effect
    const p2 = percent(alpha,.1,1);
    x.setLineDash([99*p2,99]);

    // cab top
    rect(7,16,18,-8,color(2,2));
    rect(7,8,18,4,color(2,3));
    rect(25,8,8,8,color(2,1));
    rect(25,8,-18,8);
    rect(25,8,8,8);

    // cab
    rect(25,16,7,23,color());
    rect(11,39,14,-23,color(1,1));
    rect(11,16,14,18,color(1,2));
    rect(11,16,14,8,color(1,3));
    rect(25,16,-14,24);

    // cab window
    rect(15,29,6,-9,color(2,2));
    circle(15,21,5,0,PI/2,color(2,4),1);
    rect(21,21,-6,9);

    // little stack
    rect(37,14,9,6,color(3,2));
    rect(37,14,4.5,6,color(3,3));
    rect(37,14,9,6);

    // big stack
    rect(50,20,10,-8,color(0,1));
    rect(50,20,6.5,-8,color(0,2));
    rect(50,20,3.5,-8,color(0,3));
    rect(50,20,10,-8);
    circle(55,2,11.4,.5,PI-.5,color(3,3));
    circle(55,2,11.4,.5,PI/2,color(3,2),1);
    circle(55,2,11.4,.5,PI-.5);
    rect(45,7,20,-7,color(0,2));
    rect(45,-1,20,4,color(0,3));
    rect(45,-1,20,8);

    // engine
    for (let i=5; i--;)
    {
        // stagger radius to fix slight seam
        circle(60-i*6,30, 9.9,0,2*PI,color(i+2,3));
        circle(60-i*6,30,10.0,-.5,PI+.5,color(i+2,2));
        circle(60-i*6,30,10.1,.5,PI-.5,color(i+2,1));
    }

    // engine outline
    circle(36,30,10,PI/2,PI*3/2);
    circle(48,30,10,PI/2,PI*3/2);
    circle(60,30,10);
    line(36,20,60,20);

    // engine front light
    circle(60,30,4,PI,3*PI,color(3,2)); 
    circle(60,30,4,PI,2*PI,color(3,3));
    circle(60,30,4,PI,3*PI);

    // front brush
    for (let i=6; i--;)
    {
        x.beginPath();
        x.lineTo(53,54);
        x.lineTo(53,40);
        x.lineTo(53+(1+i*2.9)*p,40);
        x.lineTo(53+(4+i*3.5)*p,54);
        x.fillStyle = color(0,i%2+2);
        x.fill();
        i%2 && x.stroke();
    }

    // wheels
    rect(6,40,5,5);
    rect(6,40,5,5,color());
    rect(15,54,38,-14,color());
    for (let i=3; i--;)
    for (let j=2; j--;)
    {
        circle(15*i+15,47,j?7:1,PI,3*PI,color(i,3));
        x.stroke();
        circle(15*i+15,47,j?7:1,0,PI,color(i,2));
        x.stroke();
    }
    line(6,40,68,40); // center
    line(77,54,4,54); // bottom

    // draw engine name
    const s = engineName;
    x.font = '900 16px arial';
    x.textAlign = 'center';
    x.textBaseline = 'top';
    x.lineWidth = .1+p*3.9;
    let w2 = 0;
    for (let i=0; i<s.length; ++i)
        w2 += x.measureText(s[i]).width;
    for (let j=2; j--;)
    for (let i=0, X=41-w2/2; i<s.length; ++i)
    {
        x.fillStyle = color(i,2);
        const w = x.measureText(s[i]).width;
        x[j?'strokeText':'fillText'](s[i],X+w/2,55.5,17*p);
        X += w;
    }
    
    x.restore();
}