/* Shared styles for the Information Theory Lab site. */

:root {
    --ink: #111111;
    --ink-soft: #4a4a4a;
    --ink-faint: #8a8a8a;
    --rule: #e4e4e4;
    --paper: #ffffff;
    --paper-alt: #f7f7f5;
    --crimson: #a41034;

    --serif: 'Source Serif 4', Georgia, serif;
    --sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Helvetica Neue', sans-serif;
    --code: 'JetBrains Mono', ui-monospace, Menlo, monospace;  /* wordmark and binary text only */
    --label: var(--sans);                                       /* small labels, links, dates */

    --max: 1440px;
    --gutter: clamp(16px, 4vw, 48px);
}

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

html { -webkit-text-size-adjust: 100%; }

body {
    margin: 0;
    background: var(--paper);
    color: var(--ink);
    font-family: var(--sans);
    font-size: 17px;
    line-height: 1.6;
    -webkit-font-smoothing: antialiased;
}

a { color: inherit; }
img { max-width: 100%; display: block; }

.wrap {
    max-width: var(--max);
    margin: 0 auto;
    padding: 0 var(--gutter);
}

/* ---------- Header ---------- */

.site-header {
    position: sticky;
    top: 0;
    z-index: 50;
    background: rgba(255, 255, 255, 0.92);
    backdrop-filter: saturate(180%) blur(8px);
    border-bottom: 1px solid var(--rule);
}

.site-header .wrap {
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 64px;
}

.wordmark {
    font-family: var(--code);
    font-size: 16px;
    letter-spacing: -0.03em;
    color: var(--ink);
    text-decoration: none;
}

.wordmark-accent {
    color: var(--crimson);
}

.wordmark-at { color: var(--ink); }

.nav { display: flex; gap: 32px; }

.nav a {
    font-size: 15px;
    color: var(--ink-soft);
    text-decoration: none;
    transition: color 0.15s;
}

.nav a:hover, .nav a[aria-current="page"] { color: var(--ink); }

.nav-toggle {
    display: none;
    background: none;
    border: 0;
    padding: 8px;
    margin-right: -8px;
    cursor: pointer;
    color: var(--ink);
}

@media (max-width: 760px) {
    .nav-toggle { display: block; }
    .nav {
        display: none;
        position: absolute;
        top: 64px;
        left: 0;
        right: 0;
        flex-direction: column;
        gap: 0;
        background: var(--paper);
        border-bottom: 1px solid var(--rule);
        padding: 8px var(--gutter) 16px;
    }
    .nav.open { display: flex; }
    .nav a { padding: 10px 0; font-size: 17px; }
}

/* ---------- Type ---------- */

.display {
    font-family: var(--serif);
    font-weight: 400;
    font-size: clamp(44px, 7vw, 88px);
    line-height: 1.02;
    letter-spacing: -0.025em;
    margin: 0;
}

.lede {
    font-size: clamp(19px, 2vw, 23px);
    line-height: 1.5;
    color: var(--ink-soft);
    max-width: 38em;
    margin: 0;
}

h2.section-title {
    font-family: var(--serif);
    font-weight: 400;
    font-size: clamp(30px, 3.6vw, 44px);
    line-height: 1.12;
    letter-spacing: -0.02em;
    margin: 0;
}

h3 {
    font-family: var(--serif);
    font-weight: 400;
    font-size: 26px;
    line-height: 1.2;
    letter-spacing: -0.01em;
    margin: 0;
}

/* Binary text: fixed-width digits so decoding doesn't reflow the line. */
.binary {
    font-family: var(--code);
    font-feature-settings: "zero" 0;
}

/* ---------- Sections ---------- */

.section { padding: clamp(40px, 5vw, 64px) 0; }
.section.alt { background: var(--paper-alt); }

/* Label bar that sits above each section; its label decodes from bits. */
.bar {
    display: flex;
    align-items: baseline;
    gap: 16px;
    padding-bottom: 14px;
    margin-bottom: clamp(32px, 5vw, 56px);
    border-bottom: 1px solid var(--ink);
    font-family: var(--label);
    font-size: 13px;
    letter-spacing: 0.04em;
    text-transform: uppercase;
}

.bar .bar-index { color: var(--crimson); }
.bar .bar-link {
    margin-left: auto;
    text-transform: none;
    letter-spacing: 0;
    text-decoration: none;
    color: var(--ink-soft);
}
.bar .bar-link:hover { color: var(--ink); }

.arrow-link {
    text-decoration: none;
    border-bottom: 1px solid currentColor;
    padding-bottom: 1px;
}
.arrow-link::after { content: " \2192"; }

/* Section headings that hang in the left margin, outside the text column.
   A page opts in with <body class="margin-page">: its .section content is indented by
   --margin-w, and .margin-label headings sit in that space at the page edge. */
.margin-page { --margin-w: 0px; }
.margin-layout { display: grid; grid-template-columns: 1fr; gap: 24px; }
.margin-label {
    margin: 0;
    font-family: var(--serif);
    font-weight: 600;
    font-size: 26px;
    line-height: 1.15;
    letter-spacing: -0.01em;
    color: var(--crimson);
}
.margin-label a {
    display: block;
    margin-top: 10px;
    font-family: var(--label);
    font-weight: 400;
    font-size: 14px;
    letter-spacing: 0;
    color: var(--ink);
    text-decoration: none;
}
.margin-label a:hover { color: var(--crimson); }

@media (min-width: 1100px) {
    .margin-page { --margin-w: 260px; }
    .margin-page main .section .wrap { padding-left: calc(var(--gutter) + var(--margin-w)); }
    .margin-layout {
        grid-template-columns: var(--margin-w) 1fr;
        gap: 0;
        margin-left: calc(-1 * var(--margin-w));
    }
    .margin-label {
        position: sticky;
        top: 96px;
        align-self: start;
        padding-right: 24px;
        padding-top: 14px;  /* sit on the baseline of the larger content titles */
        font-size: 28px;
    }
}

/* ---------- Footer ---------- */

.site-footer {
    border-top: 1px solid var(--rule);
    padding: 40px 0 32px;
    font-size: 15px;
    color: var(--ink-soft);
}

.site-footer .cols {
    display: grid;
    grid-template-columns: 2fr 1fr 1fr;
    gap: 32px;
}

.site-footer .footer-title {
    font-family: var(--serif);
    font-size: 19px;
    color: var(--ink);
    margin-bottom: 8px;
}

.site-footer .footer-title .accent { color: var(--crimson); }

.site-footer ul { list-style: none; margin: 0; padding: 0; }
.site-footer li { margin: 4px 0; }
.site-footer a { text-decoration: none; }
.site-footer a:hover { color: var(--ink); }

.site-footer .fineprint {
    margin-top: 48px;
    font-size: 13px;
    color: var(--ink-faint);
}

@media (max-width: 760px) {
    .site-footer .cols { grid-template-columns: 1fr; }
}