demo.css

:root {
    --font: 'Source Sans Pro', sans-serif;

    --color-bg: hsl(0, 0%, 93%);
    --color-fg: hsl(0, 0%, 100%);
    --color-primary: 211, 69%, 57%;

    --code-font: 'Source Code Pro', monospace;
    --code-base: hsl(0, 0%, 0%);
    --code-tagname: hsl(195, 100%, 33%);
    --code-keyword: hsl(217, 100%, 50%);
    --code-string: hsl(0, 77%, 36%);
}

*, *::before, *::after {
    box-sizing: border-box;
    margin-top: 0;
}

body {
    font-family: var(--font);
    padding: 0.5em;
    background: var(--color-bg);
}

main, footer {
    max-width: 50rem;
    margin: auto;
}

h1 {
    font-size: 3em;
    font-weight: bold;
    text-align: center;
}

footer {
    text-align: center;
    padding: 1.5em;
}

button, ::part(button) {
    font-family: var(--font);
    font-size: 0.75em;
    border-radius: 0.25em;
    border: none;
    padding: 0.625em 1.125em;
    color: var(--color-fg);
    text-transform: uppercase;
    letter-spacing: 0.0625em;
    box-shadow: 0 0.25em 0.25em -0.125em rgba(0, 0, 0, 0.25);
    cursor: pointer;
    background: hsl(var(--color-primary));
}

button:hover, ::part(button):hover {
    box-shadow: 0 0.25em 0.25em -0.125em rgba(0, 0, 0, 0.25), 0 0 0 3em rgba(0, 0, 0, 0.2) inset;
}

button:active, ::part(button):active, button[disabled] {
    box-shadow: 0 0 0 3em rgba(0, 0, 0, 0.3) inset;
}

button[disabled] {
    pointer-events: none;
    opacity: 0.5;
}

figure {
    font-size: 1.5em;
    background-color: var(--color-fg);
    padding: 1em;
    border-radius: 0.25em;
    border: 0.0625em solid hsla(var(--color-primary), 1);
    box-shadow: 0.125em 0.125em 0.25em hsla(0, 0%, 0%, 0.15) inset;
    position: relative;
    margin: 0 0 1rem;
}

figure button {
    position: absolute;
    font-size: 0.667em;
    bottom: 0.25em;
    right: 0.25em;
}

pre {
    white-space: break-spaces;
}

pre code {
    display: block;
    font-size: 1.125em;
    padding: 0.75em;
    background-color: hsl(210, 11%, 4%);
    border-radius: 0.25em;
    color: hsl(60, 30%, 96%);
    line-height: 1.5;
    border: 0.125em solid hsl(0, 0%, 47%);
}

code mark {
    background: none;
    color: hsl(120, 47%, 65%);
}

code mark strong {
    color:hsl(23, 95%, 52%);
}

.demo {
    margin-bottom: 6rem;
}

.demo typewritten-text[paused] .typewritten-text_character::after {
    visibility: hidden;
}

.special {
    font-size: 1.25em;
    color:hsl(0, 77%, 36%);
}