/* Inference Engineering Distilled — low-contrast Neo-Brutalist Blueprint */
:root {
    --bg: #fdfcf8;
    --bg-warm: #f6f3ea;
    --paper: #ffffff;
    --ink: #3a362e;
    --muted: #625d53;
    --muted-quiet: #726d5f;
    --line: #8e887a;
    --line-soft: #ded8c9;
    --grid-line: #f2f0e8;
    --blue: #4f79c8;
    --blue-deep: #355f9f;
    --red: #b46256;
    --green: #5f8468;
    --yellow: #f6e6ae;
    --tint-blue: #eef3fa;
    --tint-red: #faf0ed;
    --tint-green: #eef4ef;
    --tint-yellow: #fbf5e2;
    --tint-neutral: #f7f5ee;
    --shadow: rgba(58, 54, 46, 0.14);
    --sans: "Space Grotesk", system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
    --mono: "JetBrains Mono", ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
    --measure: 74ch;
    --shell: 1220px;
}

* { box-sizing: border-box; }
html { color-scheme: light; scroll-padding-top: 5rem; }
body {
    margin: 0;
    color: var(--ink);
    background-color: var(--bg);
    background-image:
        linear-gradient(var(--grid-line) 1px, transparent 1px),
        linear-gradient(90deg, var(--grid-line) 1px, transparent 1px);
    background-size: 34px 34px;
    font-family: var(--sans);
    font-size: 1rem;
    line-height: 1.65;
    -webkit-font-smoothing: antialiased;
}
html[lang^="zh"] body {
    font-family: "Noto Sans TC", "PingFang TC", "Microsoft JhengHei", "Hiragino Sans TC",
        system-ui, sans-serif;
    line-height: 1.78;
    letter-spacing: 0.012em;
}

[hidden] { display: none !important; }
a { color: var(--blue-deep); text-underline-offset: 0.18em; }
a:hover { text-decoration-thickness: 0.14em; }
button, input { color: inherit; font: inherit; }
p { margin: 0 0 1em; max-width: var(--measure); text-wrap: pretty; }
h1, h2, h3 { text-wrap: balance; }
code { font-family: var(--mono); }

:focus-visible {
    outline: 3px solid var(--blue-deep);
    outline-offset: 3px;
}

.skip-link {
    position: fixed;
    z-index: 1000;
    top: 0.5rem;
    left: 0.5rem;
    padding: 0.7rem 1rem;
    border: 2px solid var(--line);
    background: var(--ink);
    color: var(--paper);
    font-weight: 700;
    transform: translateY(-160%);
}
.skip-link:focus { transform: translateY(0); }

.site-header {
    border-bottom: 2px solid var(--line);
    background: color-mix(in srgb, var(--bg) 94%, transparent);
}
.site-header nav {
    width: min(var(--shell), calc(100% - 2rem));
    min-height: 4rem;
    margin: 0 auto;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 1rem;
}
.site-title {
    color: var(--ink);
    font-weight: 700;
    letter-spacing: -0.02em;
    text-decoration: none;
}
.language-switch {
    display: inline-flex;
    align-items: center;
    min-height: 2.5rem;
    padding: 0.35rem 0.75rem;
    border: 2px solid var(--line);
    background: var(--paper);
    box-shadow: 3px 3px 0 var(--shadow);
    color: var(--ink);
    font-family: var(--mono);
    font-size: 0.75rem;
    font-weight: 700;
    text-decoration: none;
}
.site-header-actions {
    display: inline-flex;
    align-items: center;
    gap: 0.6rem;
}
/* Same pill as the language switch, tinted so the ask reads as an invitation
   rather than another navigation control. It sits under the page title in the
   hero, not in the nav bar, so the persistent chrome stays navigation-only. */
.hero-star {
    display: inline-flex;
    align-items: center;
    gap: 0.45rem;
    min-height: 2.75rem;
    margin-top: 1.6rem;
    padding: 0.35rem 0.9rem;
    border: 2px solid var(--line);
    background: var(--tint-yellow);
    box-shadow: 3px 3px 0 var(--shadow);
    color: var(--ink);
    font-family: var(--mono);
    font-size: 0.75rem;
    font-weight: 700;
    text-decoration: none;
}
.star-glyph { color: var(--red); font-size: 0.95rem; line-height: 1; }

/* Catalogue */
.catalogue, .unit {
    width: min(var(--shell), calc(100% - 2rem));
    margin: 0 auto;
    padding-bottom: 5rem;
}
.catalogue-hero {
    position: relative;
    padding: clamp(3rem, 8vw, 7rem) 0 clamp(2.2rem, 5vw, 4rem);
}
.catalogue-hero::after {
    content: "";
    position: absolute;
    right: 1rem;
    bottom: 2rem;
    width: clamp(4rem, 11vw, 8rem);
    aspect-ratio: 1;
    border: 2px solid var(--line);
    background: var(--tint-blue);
    box-shadow: 9px 9px 0 var(--shadow);
    transform: rotate(4deg);
    z-index: -1;
}
.catalogue-hero .eyebrow, .unit-number {
    font-family: var(--mono);
    font-size: 0.75rem;
    font-weight: 700;
    letter-spacing: 0.12em;
    text-transform: uppercase;
    color: var(--muted-quiet);
}
.catalogue-hero h1 {
    max-width: 16ch;
    margin: 0.6rem 0 1rem;
    font-size: clamp(2.5rem, 7vw, 5.5rem);
    line-height: 0.96;
    letter-spacing: -0.045em;
    text-transform: uppercase;
}
html[lang^="zh"] .catalogue-hero h1 { line-height: 1.12; letter-spacing: 0; text-transform: none; }
/* Class-based, not :last-child — the hero star pill now follows the deck. */
.catalogue-hero .deck { color: var(--muted); font-size: clamp(1rem, 2vw, 1.2rem); }

.catalogue-filters {
    position: sticky;
    top: 0;
    z-index: 20;
    margin-bottom: 2rem;
    border-block: 2px solid var(--line);
    background: var(--bg);
}
.filter-toggle, .toc-toggle {
    display: none;
    width: 100%;
    align-items: center;
    justify-content: space-between;
    min-height: 3rem;
    padding: 0.65rem 0.85rem;
    border: 2px solid var(--line);
    background: var(--paper);
    box-shadow: 3px 3px 0 var(--shadow);
    cursor: pointer;
    font-family: var(--mono);
    font-size: 0.75rem;
    font-weight: 700;
    letter-spacing: 0.06em;
    text-transform: uppercase;
}
.filter-panel {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 1rem;
    padding: 0.8rem 0;
}
.filter-panel > p { flex: 0 0 auto; margin: 0; color: var(--muted); font-family: var(--mono); font-size: 0.75rem; }
.filter-chips { display: flex; flex-wrap: wrap; gap: 0.5rem; }
.topic-chip {
    min-height: 2.25rem;
    padding: 0.35rem 0.7rem;
    border: 2px solid var(--line);
    background: var(--paper);
    box-shadow: 2px 2px 0 var(--shadow);
    cursor: pointer;
    font-family: var(--mono);
    font-size: 0.75rem;
    font-weight: 700;
}
.topic-chip:hover { background: var(--tint-blue); }
.topic-chip[aria-pressed="true"] { background: var(--yellow); }

.catalogue-spine { position: relative; padding-left: 2rem; }
.catalogue-spine::before {
    content: "";
    position: absolute;
    top: 0;
    bottom: 0;
    left: 0.55rem;
    width: 2px;
    background: var(--line);
}
.catalogue-grid {
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 1.1rem;
    margin: 0;
    padding: 0;
    list-style: none;
}
.catalogue-card {
    position: relative;
    min-width: 0;
    border: 2px solid var(--line);
    background: var(--paper);
    box-shadow: 4px 4px 0 var(--shadow);
}
.catalogue-card::before {
    content: "";
    position: absolute;
    top: 1.4rem;
    left: -2rem;
    width: 0.85rem;
    height: 0.85rem;
    border: 2px solid var(--line);
    background: var(--yellow);
}
.catalogue-card > a { display: block; height: 100%; padding: 1.2rem 1.3rem; color: inherit; text-decoration: none; }
.catalogue-card h2 { margin: 0.35rem 0 0.5rem; font-size: clamp(1.15rem, 2vw, 1.4rem); line-height: 1.2; }
.catalogue-card p { color: var(--muted); }
.catalogue-card-facts { display: flex; flex-wrap: wrap; justify-content: space-between; gap: 0.5rem; font-family: var(--mono); font-size: 0.75rem; }
.catalogue-card:hover { background: var(--tint-blue); transform: translate(2px, 2px); box-shadow: 2px 2px 0 var(--shadow); }
.tags { display: flex; flex-wrap: wrap; gap: 0.35rem; margin: 1rem 0 0; padding: 0; list-style: none; }
.tags li {
    padding: 0.18rem 0.45rem;
    border: 1px solid var(--line);
    background: var(--tint-neutral);
    font-family: var(--mono);
    font-size: 0.75rem;
}

/* Unit shell */
.breadcrumb { display: flex; flex-wrap: wrap; align-items: center; gap: 0.7rem; padding-top: 1.25rem; color: var(--muted); font-family: var(--mono); font-size: 0.75rem; }
.breadcrumb span::before { content: "/"; padding-right: 0.7rem; color: var(--line); }
.chapter-hero { padding: clamp(2.2rem, 6vw, 4.5rem) 0 2.2rem; border-bottom: 2px solid var(--line); }
.chapter-hero h1 { max-width: 22ch; margin: 0.5rem 0 0.8rem; font-size: clamp(2rem, 5vw, 4rem); line-height: 1.02; letter-spacing: -0.035em; }
html[lang^="zh"] .chapter-hero h1 { line-height: 1.22; letter-spacing: 0; }
.chapter-hero .deck { color: var(--muted); font-size: clamp(1rem, 1.7vw, 1.15rem); }
.chapter-facts { display: flex; flex-wrap: wrap; gap: 0.55rem; margin-top: 1.3rem; }
.chapter-facts p {
    margin: 0;
    padding: 0.3rem 0.6rem;
    border: 2px solid var(--line);
    background: var(--paper);
    font-family: var(--mono);
    font-size: 0.75rem;
    font-weight: 700;
}
.unit-layout { display: grid; grid-template-columns: minmax(0, 1fr) 17rem; gap: 2.2rem; align-items: start; padding-top: 2rem; }
.unit-body { min-width: 0; }
.unit-body > section, .categorized-reading-map > section, .glossary-shell > section { max-width: 52rem; margin: 0 0 2.4rem; scroll-margin-top: 5rem; }
.unit-body section > h2, .categorized-reading-map > h2 {
    display: flex;
    gap: 0.5rem;
    margin: 0 0 0.9rem;
    color: var(--muted);
    font-family: var(--mono);
    font-size: 0.78rem;
    letter-spacing: 0.1em;
    text-transform: uppercase;
}
.unit-body section > h2::before, .categorized-reading-map > h2::before { content: "//"; color: var(--blue); }
html[lang^="zh"] .unit-body section > h2 { letter-spacing: 0.06em; text-transform: none; }

.unit-aside { position: sticky; top: 1rem; align-self: start; }
.toc-panel, .source-map-panel, .reading-guide {
    border: 2px solid var(--line);
    background: var(--paper);
    box-shadow: 4px 4px 0 var(--shadow);
    padding: 1rem;
}
.toc h2, .source-map-panel > h2, .reading-guide > h2 {
    margin: 0 0 0.7rem;
    color: var(--muted);
    font-family: var(--mono);
    font-size: 0.75rem;
    letter-spacing: 0.1em;
    text-transform: uppercase;
}
.toc ol { display: grid; gap: 0.12rem; margin: 0; padding: 0; list-style: none; }
.toc a { display: block; padding: 0.35rem 0.45rem; border-left: 3px solid var(--line-soft); color: var(--muted); font-size: 0.85rem; text-decoration: none; }
.toc a:hover, .toc a.is-current { border-left-color: var(--blue); background: var(--tint-blue); color: var(--ink); }

.content-block {
    max-width: var(--measure);
    margin: 0 0 1.15rem;
    border: 0;
    background: transparent;
    box-shadow: none;
    padding: 0;
}
.block-callout, .block-formula, .block-visual-ref, #tldr > .block-paragraph:first-of-type {
    border: 2px solid var(--line);
    box-shadow: 3px 3px 0 var(--shadow);
    padding: 1rem 1.1rem;
}
#tldr > .block-paragraph:first-of-type { background: var(--tint-blue); }
.block-callout { background: var(--tint-yellow); }
.block-formula { background: var(--tint-green); }
.content-block > p:last-child, .content-block aside > p:last-child { margin-bottom: 0; }
.bullets, .steps, .source-list { display: grid; gap: 0.7rem; margin: 0; padding-left: 1.35rem; }
.steps > li::marker { color: var(--red); font-family: var(--mono); font-weight: 700; }
.metric-grid, .comparison-grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 0.75rem; }
.metric, .comparison-item { min-width: 0; padding: 0.85rem; border: 2px solid var(--line-soft); background: var(--paper); }
.metric h3, .comparison-item h3 { margin: 0; font-size: 0.9rem; }
.metric-value { margin: 0.25rem 0; color: var(--blue-deep); font-family: var(--mono); font-size: 1.25rem; font-weight: 700; }
.formula { margin: 0; }
.formula code { display: block; overflow-x: auto; padding: 0.75rem; border: 2px solid var(--line); background: var(--ink); color: var(--paper); }
.formula figcaption { margin-top: 0.6rem; color: var(--muted); }
.term-list { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 0.7rem; margin: 0; }
.term-entry { padding: 0.8rem; border: 2px solid var(--line-soft); background: var(--paper); }
.term-entry dt { font-family: var(--mono); font-weight: 700; }
.term-entry dd { margin: 0.35rem 0 0; color: var(--muted); }
.source-map { display: grid; gap: 0.7rem; margin: 0; }
.source-entry { padding-top: 0.7rem; border-top: 1px solid var(--line-soft); }
.source-entry dt { font-weight: 700; }
.source-entry dd { margin: 0.2rem 0 0; color: var(--muted); font-family: var(--mono); font-size: 0.75rem; }
.source-map-panel { max-width: var(--measure); margin: 0 0 2rem; background: var(--tint-neutral); }
.reading-guide { max-width: var(--measure); margin-bottom: 2rem; background: var(--tint-yellow); }

.glossary-shell { max-width: 52rem; }
.glossary-shell > label { display: block; margin-bottom: 0.35rem; font-family: var(--mono); font-size: 0.75rem; font-weight: 700; }
.glossary-shell input { width: 100%; min-height: 3rem; padding: 0.65rem 0.8rem; border: 2px solid var(--line); border-radius: 0; background: var(--paper); }
.glossary-shell > [role="status"] { margin: 0.45rem 0 1rem; color: var(--muted); font-family: var(--mono); font-size: 0.75rem; }
.glossary-index { margin-bottom: 2rem; padding: 0.7rem; border: 2px solid var(--line); background: var(--tint-blue); }
.glossary-index ul { display: flex; flex-wrap: wrap; gap: 0.5rem; margin: 0; padding: 0; list-style: none; }
.glossary-index a { font-family: var(--mono); font-size: 0.75rem; }

.chapter-pager { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 0.9rem; max-width: var(--measure); margin-top: 2.5rem; }
.chapter-pager a { display: grid; padding: 0.9rem 1rem; border: 2px solid var(--line); background: var(--paper); box-shadow: 3px 3px 0 var(--shadow); color: inherit; text-decoration: none; }
.chapter-pager a[rel="next"] { text-align: right; }
.chapter-pager span { color: var(--muted); font-family: var(--mono); font-size: 0.75rem; text-transform: uppercase; }

/* Semantic diagrams: text and relationships stay meaningful without these rules. */
.visual { margin: 0; padding: 1rem; border: 2px solid var(--line); background: var(--tint-neutral); }
.visual > figcaption { margin-bottom: 0.35rem; font-size: 1rem; font-weight: 700; }
.visual-description { color: var(--muted); font-size: 0.9rem; }
.visual-nodes { margin: 1rem 0 0; padding: 0; list-style: none; }
.visual-node { min-width: 0; padding: 0.75rem; border: 2px solid var(--line); background: var(--paper); }
.visual-node strong, .visual-node span { display: block; }
.visual-node span, .visual-node dd { color: var(--muted); font-size: 0.85rem; }
.visual-edges { margin: 0.8rem 0 0; padding-left: 1.25rem; color: var(--muted); font-family: var(--mono); font-size: 0.75rem; }
.visual-stack .visual-nodes { display: grid; gap: 0; }
.visual-stack .visual-node + .visual-node { border-top: 0; }
.visual-flow .visual-nodes, .visual-pipeline .visual-nodes { display: flex; gap: 1.6rem; overflow-x: auto; }
.visual-flow .visual-node, .visual-pipeline .visual-node { position: relative; flex: 1 0 9rem; }
.visual-flow .visual-node:not(:last-child)::after, .visual-pipeline .visual-node:not(:last-child)::after { content: "→"; position: absolute; right: -1.3rem; top: 50%; color: var(--red); font-weight: 700; }
.visual-bottleneck-map .visual-nodes { display: grid; grid-template-columns: repeat(auto-fit, minmax(9rem, 1fr)); gap: 0.7rem; }
.visual-bottleneck-map .visual-node { border-left: 0.45rem solid var(--red); }
.visual-hierarchy .visual-nodes { display: grid; gap: 0.55rem; padding-left: 1.2rem; border-left: 3px solid var(--green); }
.visual-hierarchy .visual-node:nth-child(even) { margin-left: 1.2rem; background: var(--tint-green); }
.visual-comparison .visual-nodes { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 0.8rem; }
.visual-comparison .visual-node { margin: 0; }
.visual-comparison .visual-node:nth-child(odd) { background: var(--tint-blue); }
.visual-comparison .visual-node:nth-child(even) { background: var(--tint-red); }
.visual-control-loop .visual-nodes { display: grid; grid-template-columns: repeat(auto-fit, minmax(8rem, 1fr)); gap: 1.4rem; }
.visual-control-loop .visual-node { position: relative; border-radius: 50%; text-align: center; }
.visual-control-loop .visual-node:not(:last-child)::after { content: "↻"; position: absolute; right: -1.15rem; top: 35%; color: var(--green); font-size: 1.2rem; }

/* Interactive navigation targets stay comfortably tappable at every viewport. */
.site-title, .language-switch, .topic-chip, .toc a, .glossary-index a, .breadcrumb a {
    min-height: 2.75rem;
}
.site-title, .toc a, .glossary-index a, .breadcrumb a {
    display: inline-flex;
    align-items: center;
}
.toc a { width: 100%; }

/* The topic filter is a disclosure at every width, so the catalogue opens on units. */
.js .filter-toggle { display: flex; }
.catalogue-filters.is-open .filter-toggle span { transform: rotate(45deg); }

/* Attribution rail: where the material came from and who assembled it. */
.site-footer {
    width: min(var(--shell), calc(100% - 2rem));
    margin: 0 auto;
    padding: 2rem 0 3rem;
    border-top: 2px solid var(--line);
    color: var(--muted);
}
.site-footer h2 {
    margin: 0 0 0.6rem;
    color: var(--ink);
    font-family: var(--mono);
    font-size: 0.75rem;
    font-weight: 700;
    letter-spacing: 0.06em;
    text-transform: uppercase;
}
html[lang^="zh"] .site-footer h2 { text-transform: none; }
.footer-source p { max-width: var(--measure); margin: 0; font-size: 0.9rem; }
.footer-credit, .footer-license {
    font-family: var(--mono);
    font-size: 0.75rem;
    letter-spacing: 0.04em;
}
.footer-credit { margin: 1.4rem 0 0; }
.footer-license { margin: 0.45rem 0 0; }
.star-block {
    margin: 1.6rem 0 0;
    padding: 1.25rem 1.35rem;
    border: 2px solid var(--line);
    background: var(--paper);
    box-shadow: 4px 4px 0 var(--shadow);
}
.star-block p { max-width: var(--measure); margin: 0 0 1rem; font-size: 0.9rem; }
.star-cta {
    display: inline-flex;
    align-items: center;
    gap: 0.55rem;
    min-height: 2.75rem;
    padding: 0.5rem 1rem;
    border: 2px solid var(--line);
    background: var(--tint-yellow);
    box-shadow: 3px 3px 0 var(--shadow);
    color: var(--ink);
    font-family: var(--mono);
    font-size: 0.75rem;
    font-weight: 700;
    letter-spacing: 0.04em;
    text-decoration: none;
}

@media (max-width: 1080px) {
    .unit-layout { display: flex; flex-direction: column; align-items: stretch; gap: 0; }
    .unit-aside { order: -1; align-self: stretch; margin-bottom: 1.5rem; }
    .js .unit-aside { position: sticky; top: 0; z-index: 30; }
    .js .toc-toggle { display: flex; }
    .js .toc-panel { position: absolute; top: 100%; left: 0; right: 0; max-height: calc(100dvh - 4rem); overflow-y: auto; box-shadow: none; }
    .js .filter-panel { position: absolute; top: 100%; left: 0; right: 0; display: block; max-height: calc(100dvh - 4rem); overflow-y: auto; padding: 0.8rem; border: 2px solid var(--line); background: var(--bg); box-shadow: 4px 4px 0 var(--shadow); }
    .toc-panel .toc ol { grid-template-columns: repeat(auto-fit, minmax(10rem, 1fr)); }
    .catalogue-filters { top: 0; }
    .unit-aside.is-open .toc-toggle span { transform: rotate(45deg); }
    .unit-body > section, .categorized-reading-map > section, .glossary-shell > section { scroll-margin-top: 4.5rem; }
}

@media (max-width: 640px) {
    .catalogue, .unit, .site-footer { width: min(100% - 1.1rem, var(--shell)); }
    .catalogue-grid { grid-template-columns: 1fr; }
    .catalogue-spine { padding-left: 1.5rem; }
    .catalogue-card::before { left: -1.5rem; }
    .catalogue-hero::after { opacity: 0.45; }
    .metric-grid { grid-template-columns: 1fr; }
    .comparison-grid, .term-list, .visual-comparison .visual-nodes { grid-template-columns: 1fr; }
    .visual-flow .visual-nodes, .visual-pipeline .visual-nodes { flex-direction: column; overflow: visible; }
    .visual-flow .visual-node:not(:last-child)::after, .visual-pipeline .visual-node:not(:last-child)::after { content: "↓"; right: 50%; top: auto; bottom: -1.45rem; }
    .visual-control-loop .visual-nodes { grid-template-columns: 1fr; }
    .visual-control-loop .visual-node { border-radius: 0; }
    .visual-control-loop .visual-node:not(:last-child)::after { right: 50%; top: auto; bottom: -1.35rem; }
    .chapter-pager { grid-template-columns: 1fr; }
    .chapter-pager a[rel="next"] { text-align: left; }
}

@media (prefers-reduced-motion: reduce) {
    *, *::before, *::after { scroll-behavior: auto !important; transition-duration: 0.001ms !important; animation-duration: 0.001ms !important; animation-iteration-count: 1 !important; }
}

@media print {
    @page { margin: 18mm; }
    body { background: #fff; color: #000; font-size: 10.5pt; }
    .site-header, .skip-link, .catalogue-filters, .unit-aside, .chapter-pager, .language-switch, .star-block, .glossary-shell > label, .glossary-shell > input, .glossary-shell > [role="status"] { display: none !important; }
    .catalogue, .unit { width: 100%; padding: 0; }
    .site-footer { width: 100%; }
    .unit-layout { display: block; }
    .content-block, .catalogue-card, .visual, .reading-guide, .source-map-panel { break-inside: avoid; box-shadow: none; }
    a { color: inherit; text-decoration: none; }
}