/* via https://codepen.io/argyleink/pen/qBRpdEr */
html {
    scroll-snap-type: y mandatory;
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol";
}

body {
    margin: 0;
    counter-reset: slides;
}

img {
    display: block;
    max-width: 100%;
    height: auto;
}

@keyframes scroll {
    0% {
        transform: translateY(-10px);
    }
    50% {
        transform: translateY(0px);
    }
    100% {
        transform: translateY(-10px);
    }
}

@keyframes fadeout {
    from {
        opacity: 1;
    }
    to {
        opacity: 0;
    }
}

body > section::before {
    counter-increment: slides;
    content: '# ' counter(slides);
    position: absolute;
    font-weight: 700;
    left: 1rem;
    top: 1rem;
}

section {
    position: relative;
    scroll-snap-align: start;
    min-block-size: 100vh;
    
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    background: var(--slide-background, white);
    background-size: var(--slide-background-size, contain);
    background-position: center;
    background-repeat: no-repeat;
    color: var(--slide-text, black);
}

body[data-help] section::after {
    content: '';
    background-color: currentColor;
    -webkit-mask-image: url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24"><path d="M16 2c1.103 0 2 .897 2 2v12c0 3.309-2.691 6-6 6s-6-2.691-6-6v-12c0-1.103.897-2 2-2h8zm4 2c0-2.209-1.791-4-4-4h-8c-2.209 0-4 1.791-4 4v12c0 4.418 3.582 8 8 8s8-3.582 8-8v-12zm-7 1c0-.552-.447-1-1-1s-1 .448-1 1v4c0 .552.447 1 1 1s1-.448 1-1v-4z"/></svg>');
    mask-image: url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24"><path d="M16 2c1.103 0 2 .897 2 2v12c0 3.309-2.691 6-6 6s-6-2.691-6-6v-12c0-1.103.897-2 2-2h8zm4 2c0-2.209-1.791-4-4-4h-8c-2.209 0-4 1.791-4 4v12c0 4.418 3.582 8 8 8s8-3.582 8-8v-12zm-7 1c0-.552-.447-1-1-1s-1 .448-1 1v4c0 .552.447 1 1 1s1-.448 1-1v-4z"/></svg>');
    width: 24px;
    height: 24px;
    position: absolute;
    left: 1rem;
    bottom: 1rem;
    animation-name: scroll, fadeout;
    animation-duration: 3s, 2s;
    animation-iteration-count: 6, 1;
    animation-delay: 0ms, 15s;
    animation-fill-mode: forwards, forwards;
}

@media (prefers-reduced-motion: reduce) {
    html:focus-within {
        scroll-behavior: auto;
    }
    
    *,
    *::before,
    *::after {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
        scroll-behavior: auto !important;
    }
}