style.css

body,
html,
figure,
img,
div,
input,
textarea,
p,
h1,
h2,
h3,
h4,
h5,
h6,
ul,
li,
a,
main {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    list-style: none;
    text-decoration: none;
}

.hidden {
    display: none;
}

 :root {
    --corBackgroundPrimaria: #fffe00;
    --corBackgroundSecundaria: #333030;
    --corTextoPrimaria: #636363;
    --corTextoSecundaria: #000;
    --corLinhas: rgb(154 154 154);
}

.coluna {
    flex-basis: 49%;
}


/* BODY */

body {
    font-family: 'Open Sans', sans-serif;
}


/*HEADER */

header {
    /*background-color: var(--corBackgroundPrimaria);*/
    padding: 30px 30px 0;
    background-image: url(https://img.freepik.com/vetores-gratis/fundo-branco-abstrato_23-2148810113.jpg?size=626&ext=jpg);
}

header .container {
    background-color: white;
}

header .linha {
    align-items: center;
}

header .coluna-esquerda {
    flex-basis: 30%;
}

header .coluna-direita {
    flex-basis: 60%;
    text-align: center;
}

header .coluna img {
    max-width: 100%;
}

header .coluna h1 {
    font-size: 1.5rem;
    color: var(--corTextoSecundaria);
}

header .coluna p {
    font-size: 1rem;
    color: var(--corTextoPrimaria);
}

header .coluna ul {
    margin: 16px 0 0;
}

header .coluna ul li {
    margin: 0 0 12px;
}

header .coluna ul li a {
    font-size: 1rem;
    color: var(--corTextoSecundaria);
}


/* FOOTER */

footer {
    background-color: var(--corBackgroundSecundaria)
}

footer .container {
    padding: 20px;
}

footer nav ul li a {
    color: white;
}

footer nav .info-contato li {
    margin: 0 0 15px;
}

footer nav .redes-sociais {
    border-top: 1px solid rgb(255 255 255 / 20%);
    margin: 25px 0 50px;
    padding: 25px 0 0;
    text-align: center;
}

footer nav .redes-sociais li {
    margin: 0 15px;
    text-align: center;
    display: inline-block;
}

footer nav .redes-sociais li a img {
    width: 45px;
}


/* PAGINA INICIAL */

main .coluna {
    padding: 20px;
}

main .coluna section {
    border-bottom: 1px solid #d4e9ff;
    margin: 0 0 20px;
    min-height: 187px;
    color: var(--corTextoSecundaria)
}

main .coluna section h2 {
    font-size: 1.3rem;
    margin: 0 0 15px;
}

main .coluna section p {
    font-size: 0.9rem;
    color: var(--corTextoPrimaria);
    line-height: 1.5;
}

main .coluna section ul li {
    margin: 0 0 12px;
}

main .coluna section ul li h3 {
    font-size: 1.1rem;
}

main .coluna section ul li strong {
    font-size: 0.9rem;
    font-weight: 500;
    margin: 5px 0 10px;
    display: inline-block;
}


/* EXTRAS */

.ativar-dark {
    width: 50px;
    height: 50px;
    display: none;
}

header .container {
    position: relative;
}

label {
    position: absolute;
    top: 30px;
    right: 30px;
    width: 52px;
    height: 30px;
    background-color: black;
    border-radius: 20px;
    padding: 5px 5px;
    box-sizing: border-box;
    cursor: pointer;
}

label span {
    width: 20px;
    height: 20px;
    display: block;
    background-color: hsl(0deg 0% 81%);
    border-radius: 100%;
    transition: all ease .3s;
}

.ativar-dark:checked~.dark-mode label {
    background-color: #ffffff;
}

.ativar-dark:checked~.dark-mode label span {
    background-color: var(--corBackgroundSecundaria);
    transform: translateX(21px);
    transition: all ease .3s;
}

.ativar-dark:checked~.dark-mode {
    --corBackgroundPrimaria: #000;
    --corBackgroundSecundaria: #000;
    --corBackgroundDark: #0e0e0e;
    --corTextoPrimaria: #fff;
    --corTextoSecundaria: #fff;
}

.ativar-dark:checked~.dark-mode header .container {
    background-color: var(--corBackgroundDark);
}

.ativar-dark:checked~.dark-mode .container {
    background-color: var(--corBackgroundDark);
}

.ativar-dark:checked~.dark-mode main {
    background-color: var(--corBackgroundSecundaria);
}

.ativar-dark:checked~.dark-mode header {
    background-color: var(--corBackgroundSecundaria);
    background-image: none;
}

@keyframes aumentarLargura {
    from {
        width: 0;
    }
    to {
        width: 100%;
    }
}

@keyframes aumentarAltura {
    from {
        height: 0;
    }
    to {
        height: 100%;
    }
}


/* @MEDIA */

@media only screen and (min-width: 768px) {
    .linha {
        display: flex;
        flex-wrap: wrap;
        align-items: flex-start;
        justify-content: space-between;
    }
    footer nav .redes-sociais {
        display: flex;
        justify-content: center;
    }
    header {
        padding-top: 30px 0 0;
    }
    header .coluna img {
        max-width: 250px;
        border-radius: 100%;
    }
    .container {
        width: 100%;
        max-width: 1000px;
        margin: 0 auto;
        padding: 30px;
    }
    header .coluna-direita {
        text-align: left;
    }
    main .coluna section {
        border: 2px solid transparent;
        padding: 20px;
        position: relative;
    }
    main .coluna section span {
        position: absolute;
        display: block;
        width: 0;
        height: 0;
        border: 2px solid transparent;
    }
    main .coluna section .topo-direita {
        top: -2px;
        left: -2px;
        animation-name: aumentarLargura, aumentarAltura;
        animation-duration: 1s, 1s;
        animation-delay: 2s, 3s;
        animation-fill-mode: forwards;
        border-top-color: var(--corLinhas);
        border-right-color: var(--corLinhas);
    }
}

main .coluna section .baixo-esquerda {
    bottom: -2px;
    right: -2px;
    animation-name: aumentarLargura, aumentarAltura;
    animation-duration: 1s, 1s;
    animation-delay: 4s, 5s;
    animation-fill-mode: forwards;
    border-bottom-color: var(--corLinhas);
    border-left-color: var(--corLinhas);
}

main .coluna {
    padding: 0;
}

footer nav .redes-sociais li {
    margin: 0 14px;
    text-align: center;
    display: initial;
}

@media only screen and(mind-width: 991px) {
    header .coluna-direita {
        flex-basis: 70%;
    }
}