const STYLE_SECTION: &'static str = r#"<style>
    .line {
        counter-increment: line;
    }
    .line:before {
        content: counter(line) ": ";
        font-family: Menlo, Monaco, monospace;
        font-style: italic;
        width: 3.8em;
        display: inline-block;
        text-align: right;
        filter: opacity(50%);
        -webkit-user-select: none;
    }
    .code {
        color: #dddddd;
        background-color: #222222;
        font-family: Menlo, Monaco, monospace;
        line-height: 1.4em;
        border-bottom: 2px solid #222222;
        white-space: pre;
        display: inline-block;
    }
    .odd {
        background-color: #55bbff;
        color: #223311;
    }
    .even {
        background-color: #ee7756;
        color: #551133;
    }
    .code {
        --index: calc(var(--layer) - 1);
        padding-top: calc(var(--index) * 0.15em);
        filter:
            hue-rotate(calc(var(--index) * 25deg))
            saturate(calc(100% - (var(--index) * 2%)))
            brightness(calc(100% - (var(--index) * 1.5%)));
    }
    .annotation {
        color: #4444ff;
        font-family: monospace;
        font-style: italic;
        display: none;
        -webkit-user-select: none;
    }
    body:active .annotation {
        /* requires holding mouse down anywhere on the page */
        display: inline-block;
    }
    span:hover .annotation {
        /* requires hover over a span ONLY on its first line */
        display: inline-block;
    }
</style>"#;