* {
    margin: 0;
    padding: 0;
    border: 0;
    border-collapse: collapse;
    box-sizing: border-box;
}

html {
    background-image: linear-gradient(
        to right,
        hsl(0, 0%, 90%) 0%,
        hsl(0, 0%, 100%) 50%,
        hsl(0, 0%, 90%) 100%
    );
}

body {
    font-size: 1em;
    line-height: 1.75;
    font-family: Ubuntu, sans-serif;
}

p, ul, ol, dl, h1, h2, h3, h4, h5, h6, table, figure, figcaption {
    max-width: 40rem;
    margin: 0 auto;
}

header, footer {
    text-align: center;
    line-height: 1;
    max-width: none;
    background-color: black;
    background-image: linear-gradient(
        to right,
        hsl(0, 0%, 0%) 0%,
        hsl(0, 0%, 10%) 50%,
        hsl(0, 0%, 0%) 100%
    );
    color: white;
    padding-top: 4em;
    padding-bottom: 4em;
}

    header {
        margin-bottom: 4em;
    }

        header h1 {
            margin-bottom: 0.25em;
            font-size: 4em;
        }

        header .subtitle {
            font-size: 1.25em;
            font-style: italic;
        }

        header .credits {
            font-size: 1em;
        }

        header a:link, footer a:link, header a:visited, footer a:visited {
            color: hsl(200, 100%, 50%);
        }

    main {
        margin-bottom: 4em;
    }

    footer {
        margin-top: 4em;
        padding-top: 2em;
        padding-bottom: 2em;
    }

    footer p {
        line-height: 1.25;
    }

    footer .copyright {
        padding-top: 4em;
        background-image: url('https://mirrors.creativecommons.org/presskit/buttons/88x31/svg/by-sa.svg');
        background-repeat: no-repeat;
        background-position: center top;
        background-size: auto 3em;
    }

.toc {
    padding: 0;
    text-align: center;
}

    .toc li {
        display: inline;
        padding: 0 1em;
    }

    .toc li + li {
        border-left: 0.1em solid hsl(0, 0%, 75%);
    }

p, ul, dl {
    margin-top: 1em;
    margin-bottom: 1em;
}

h1, h2, h3, h4, h5, h6 {
    font-weight: bold;
}

h2, h3, h4, h5, h6 {
    margin-top: 2em;
}

h2 {
    font-size: 2.5em;
    text-align: center;
    max-width: 60rem;
}

h3 {
    font-size: 1.5em;
}

h4 {
    font-size: 1.25em;
}

h5 {
    font-size: 1em;
}

ul, ol, dl {
    padding-left: 3em;
    padding-right: 3em;
}

    li p, dd p {
        margin-top: 0.5em;
        margin-bottom: 0.5em;
    }

    ul li {
        list-style-type: square;
    }

    li ul, li ol {
        margin-top: 0;
        margin-bottom: 0;
    }

    dt {
        font-weight: bold;
        float: left;
        height: 1.75em;
    }

    dt:after {
        white-space: pre;
        content: ": ";
    }

strong {
    font-weight: bold;
}

em {
    font-style: italic;
}

figure.image {
    box-sizing: content-box;
    max-width: none;
    padding: 1em;
    background-color: hsl(0, 0%, 90%);
}

    figure.image img {
        display: block;
        margin: 1em auto;
    }

    figure.image figcaption ol {
        padding: 0;
    }

table {
    width: 100%;
}

    tr:nth-child(odd) {
        background-color: hsl(0, 0%, 95%);
    }

    tr:nth-child(even) {
        background-color: hsl(0, 0%, 90%);
    }

        td, th {
            padding: 0.25em 0.5em;
            border: 1px solid hsl(0, 0%, 65%);
            text-align: left;
        }

        th {
            background-color: black;
            color: white;
            border-color: black;
        }

code {
    font-family: "Ubuntu Mono", monospace;
}

    .malicious {
        color: hsl(0, 100%, 50%);
    }

    .safe {
        color: hsl(120, 75%, 50%);
    }

    .html, .string {
        color: hsl(200, 100%, 50%);
    }

    var {
        font-style: italic;
    }

    var.input {
        font-style: normal;
        font-weight: bold;
        color: hsl(30, 100%, 50%);
    }

p.code {
    line-height: 1;
    padding: 1em;
    color: white;
    border: 1px solid hsl(0, 0%, 50%);
    border-radius: 0.5em;
    background-color: black;
    background-image: linear-gradient(
        to top,
        hsl(0, 0%, 5%),
        hsl(0, 0%, 25%)
    );
    text-shadow: 0 0 0.25em black;
}

    p.code .color-1 {
        color: hsl(200, 100%, 50%);
    }

    p.code .color-2 {
        color: hsl(100, 100%, 50%);
    }

    p.code .color-3 {
        color: hsl(60, 100%, 50%);
    }

p.important {
    padding-left: 3em;
    padding-right: 3em;
    font-style: italic;
}

p.note {
    font-style: italic;
}

p.note:before {
    content: "Note: ";
    white-space: pre;
}