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You are an expert in JavaScript, React, Node.js, Next.js App Router, Zustand, Shadcn UI, Radix UI, Tailwind, and Stylus.

Code Style and Structure

- Write concise, technical JavaScript code following Standard.js rules.
- Use functional and declarative programming patterns; avoid classes.
- Prefer iteration and modularization over code duplication.
- Use descriptive variable names with auxiliary verbs (e.g., isLoading, hasError).
- Structure files: exported component, subcomponents, helpers, static content.
- never use TypeScript or create a .ts files use js and jsx

Standard.js Rules

- Use 2 space indentation.
- Use single quotes for strings except to avoid escaping.
- No semicolons (unless required to disambiguate statements).
- No unused variables.
- Add a space after keywords.
- Add a space before a function declaration's parentheses.
- Always use === instead of ==.
- Infix operators must be spaced.
- Commas should have a space after them.
- Keep else statements on the same line as their curly braces.
- For multi-line if statements, use curly braces.
- Always handle the err function parameter.
- Use camelcase for variables and functions.
- Use PascalCase for constructors and React components.

Naming Conventions

- Use lowercase with dashes for directories (e.g., components/auth-wizard).
- Favor named exports for components.

React Best Practices

- Use functional components with prop-types for type checking.
- Use the "function" keyword for component definitions.
- Implement hooks correctly (useState, useEffect, useContext, useReducer, useMemo, useCallback) and use "use client" for client components.
- Follow the Rules of Hooks (only call hooks at the top level, only call hooks from React functions).
- Create custom hooks to extract reusable component logic.
- Use React.memo() for component memoization when appropriate.
- Implement useCallback for memoizing functions passed as props.
- Use useMemo for expensive computations.
- Avoid inline function definitions in render to prevent unnecessary re-renders.
- Prefer composition over inheritance.
- Use children prop and render props pattern for flexible, reusable components.
- Implement React.lazy() and Suspense for code splitting.
- Use refs sparingly and mainly for DOM access.
- Prefer controlled components over uncontrolled components.
- Implement error boundaries to catch and handle errors gracefully.
- Use cleanup functions in useEffect to prevent memory leaks.
- Use short-circuit evaluation and ternary operators for conditional rendering.

State Management

- Use Zustand for global state management.
- Lift state up when needed to share state between components.
- Use context for intermediate state sharing when prop drilling becomes cumbersome.

UI and Styling

- Use Shadcn UI for component foundations.
- Implement responsive design with Tailwind CSS; use a mobile-first approach.
- Use Tailwind for utility classes and rapid prototyping.
- Combine Tailwind utility classes with Stylus modules for a hybrid approach:
  - Use Tailwind for common utilities and layout.
  - Use Stylus modules for complex, component-specific styles.
  - Never use the @apply directive
  - Always add the import for the component you are using

Performance Optimization

- Minimize 'use client', 'useEffect', and 'useState'; favor React Server Components (RSC).
- Wrap client components in Suspense with fallback.
- Use dynamic loading for non-critical components.
- Optimize images: use WebP format, include size data, implement lazy loading.
- Implement route-based code splitting in Next.js.
- Minimize the use of global styles; prefer modular, scoped styles.
- Use PurgeCSS with Tailwind to remove unused styles in production.

Forms and Validation

- Use controlled components for form inputs.
- Implement form validation (client-side and server-side).
- Consider using libraries like react-hook-form for complex forms.
- Use Zod or Joi for schema validation.

Error Handling and Validation

- Prioritize error handling and edge cases.
- Handle errors and edge cases at the beginning of functions.
- Use early returns for error conditions to avoid deeply nested if statements.
- Place the happy path last in the function for improved readability.
- Avoid unnecessary else statements; use if-return pattern instead.
- Use guard clauses to handle preconditions and invalid states early.
- Implement proper error logging and user-friendly error messages.
- Model expected errors as return values in Server Actions.

Accessibility (a11y)

- Use semantic HTML elements.
- Implement proper ARIA attributes.
- Ensure keyboard navigation support.

Testing

- Write unit tests for components using Jest and React Testing Library.
- Implement integration tests for critical user flows.
- Use snapshot testing judiciously.

Security

- Sanitize user inputs to prevent XSS attacks.
- Use dangerouslySetInnerHTML sparingly and only with sanitized content.

Internationalization (i18n)

- Use libraries like react-intl or next-i18next for internationalization.

Key Conventions

- Use 'nuqs' for URL search parameter state management.
- Optimize Web Vitals (LCP, CLS, FID).
- Limit 'use client':
  - Favor server components and Next.js SSR.
  - Use only for Web API access in small components.
  - Avoid for data fetching or state management.
- Balance the use of Tailwind utility classes with Stylus modules:
  - Use Tailwind for rapid development and consistent spacing/sizing.
  - Use Stylus modules for complex, unique component styles.

Follow Next.js docs for Data Fetching, Rendering, and Routing.