/* Layout concept: a lab notebook on graph paper. A table-of-contents rail on the left,
   one readable column on the right, figures set as "plates" on a faint tensor grid. */
:root {
  --bg: #f5f7f5;
  --surface: #ffffff;
  --surface-2: #edf1ee;
  --ink: #14212a;
  --ink-2: #3b4954;
  --muted: #64717b;
  --rule: #d6dddd;
  --grid: rgba(20, 33, 42, 0.055);
  --accent: #d4461a;
  --accent-ink: #ffffff;
  --accent-soft: #fbe5da;
  --signal: #1b6784;
  --signal-soft: #dbecf2;
  --ok: #2b7a4c;
  --ok-soft: #dbefe2;
  --bad: #b3261e;
  --bad-soft: #f8dedb;
  --warn: #8d6100;
  --warn-soft: #f5ebcd;
  --code-bg: #111a20;
  --code-fg: #e2e8eb;
  --code-rule: #24313a;
  --tk-com: #7f8f99;
  --tk-kw: #ff9b6e;
  --tk-str: #a8d58c;
  --tk-num: #f2c66d;
  --tk-fn: #7cc7e3;
  --tk-op: #c9d2d7;
  --fig-line: #3b4954;
  --fig-box: #ffffff;
  --fig-a: #fbe0d3;
  --fig-s: #d6eaf1;
  --fig-n: #edf1ee;
  --fig-ok: #d6eedf;
  --fig-text: #14212a;
  --shadow: 0 1px 2px rgba(20, 33, 42, 0.06), 0 8px 24px rgba(20, 33, 42, 0.06);

  --f-display: "Bricolage Grotesque", "Segoe UI", system-ui, sans-serif;
  --f-body: "IBM Plex Sans", "Segoe UI", system-ui, -apple-system, sans-serif;
  --f-mono: "JetBrains Mono", ui-monospace, "Cascadia Code", Consolas, monospace;

  --fs-xs: 0.8125rem;
  --fs-sm: 0.9375rem;
  --fs-md: 1.0625rem;
  --fs-lg: 1.25rem;
  --fs-xl: 1.625rem;
  --fs-2xl: 2.125rem;
  --fs-3xl: clamp(2.25rem, 5vw, 3.5rem);

  --rail: 288px;
  --head: 60px;
  --radius: 10px;
}

@media (prefers-color-scheme:invalid) {
  :root:not([data-theme="light"]) {
    --bg: #0d1317;
    --surface: #141c21;
    --surface-2: #1a242a;
    --ink: #e2e8eb;
    --ink-2: #b5c1c7;
    --muted: #8a979f;
    --rule: #28343b;
    --grid: rgba(226, 232, 235, 0.04);
    --accent: #ff7a4a;
    --accent-ink: #1b0d07;
    --accent-soft: #3a1f15;
    --signal: #63b7d4;
    --signal-soft: #15303a;
    --ok: #6cc892;
    --ok-soft: #163326;
    --bad: #ff8a80;
    --bad-soft: #3b1c1a;
    --warn: #e3b341;
    --warn-soft: #33290f;
    --code-bg: #0a0f12;
    --code-fg: #dce3e6;
    --code-rule: #1f2a31;
    --fig-line: #b5c1c7;
    --fig-box: #141c21;
    --fig-a: #3d2117;
    --fig-s: #15323d;
    --fig-n: #1d272d;
    --fig-ok: #173427;
    --fig-text: #e2e8eb;
    --shadow: 0 1px 2px rgba(0, 0, 0, 0.3), 0 8px 24px rgba(0, 0, 0, 0.25);
    color-scheme: dark;
  }
}
:root[data-theme="dark"] {
  --bg: #0d1317;
  --surface: #141c21;
  --surface-2: #1a242a;
  --ink: #e2e8eb;
  --ink-2: #b5c1c7;
  --muted: #8a979f;
  --rule: #28343b;
  --grid: rgba(226, 232, 235, 0.04);
  --accent: #ff7a4a;
  --accent-ink: #1b0d07;
  --accent-soft: #3a1f15;
  --signal: #63b7d4;
  --signal-soft: #15303a;
  --ok: #6cc892;
  --ok-soft: #163326;
  --bad: #ff8a80;
  --bad-soft: #3b1c1a;
  --warn: #e3b341;
  --warn-soft: #33290f;
  --code-bg: #0a0f12;
  --code-fg: #dce3e6;
  --code-rule: #1f2a31;
  --fig-line: #b5c1c7;
  --fig-box: #141c21;
  --fig-a: #3d2117;
  --fig-s: #15323d;
  --fig-n: #1d272d;
  --fig-ok: #173427;
  --fig-text: #e2e8eb;
  --shadow: 0 1px 2px rgba(0, 0, 0, 0.3), 0 8px 24px rgba(0, 0, 0, 0.25);
  color-scheme: dark;
}

* { box-sizing: border-box; }
html { scroll-padding-top: calc(var(--head) + 16px); -webkit-text-size-adjust: 100%; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: var(--f-body);
  font-size: var(--fs-md);
  line-height: 1.65;
}
img, svg { max-width: 100%; }
a { color: var(--signal); text-underline-offset: 3px; }
a:hover { color: var(--accent); }
button { font: inherit; color: inherit; }
:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; border-radius: 4px; }
code { font-family: var(--f-mono); font-size: 0.88em; background: var(--surface-2); padding: 0.1em 0.38em; border-radius: 5px; }
h1, h2, h3, h4 { font-family: var(--f-display); line-height: 1.2; text-wrap: balance; margin: 0; letter-spacing: -0.01em; }
p { margin: 0; }

/* ---------- Header ---------- */
.topbar {
  position: sticky;
  top: env(safe-area-inset-top, 0px);
  z-index: 30;
  height: var(--head);
  display: flex;
  align-items: center;
  gap: 12px;
  padding-inline: 16px;
  background: color-mix(in srgb, var(--bg) 88%, transparent);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--rule);
}
.brand {
  display: flex; align-items: center; gap: 10px;
  text-decoration: none; color: var(--ink);
  font-family: var(--f-display); font-weight: 800; font-size: 1.15rem; letter-spacing: -0.02em;
  white-space: nowrap;
}
.brand:hover { color: var(--ink); }
.brand-mark { width: 30px; height: 30px; flex: none; }
.brand small { font-family: var(--f-mono); font-weight: 400; font-size: 0.7rem; color: var(--muted); letter-spacing: 0; }
.topbar .spacer { flex: 1; }
.icon-btn {
  display: inline-flex; align-items: center; justify-content: center;
  height: 36px; min-width: 36px; padding-inline: 10px;
  border: 1px solid var(--rule); border-radius: 8px;
  background: var(--surface); cursor: pointer; font-size: var(--fs-sm);
}
.icon-btn:hover { border-color: var(--ink-2); }
.icon-btn svg { width: 18px; height: 18px; }
.lang-switch { display: inline-flex; border: 1px solid var(--rule); border-radius: 8px; overflow: hidden; background: var(--surface); }
.lang-switch button {
  border: 0; background: transparent; padding: 6px 11px; cursor: pointer;
  font-family: var(--f-mono); font-size: 0.78rem; font-weight: 600; letter-spacing: 0.06em; color: var(--muted);
}
.lang-switch button[aria-pressed="true"] { background: var(--ink); color: var(--bg); }
.menu-btn { display: none; }
.search-box { position: relative; width: min(280px, 32vw); }
.search-box input {
  width: 100%; height: 36px; padding: 0 12px 0 34px;
  border: 1px solid var(--rule); border-radius: 8px; background: var(--surface); color: var(--ink);
  font: inherit; font-size: var(--fs-sm);
}
.search-box svg { position: absolute; left: 10px; top: 9px; width: 17px; height: 17px; color: var(--muted); }
.search-results {
  position: absolute; top: 42px; left: 0; right: 0; min-width: 300px;
  max-height: 60vh; overflow: auto; background: var(--surface); border: 1px solid var(--rule);
  border-radius: 10px; box-shadow: var(--shadow); padding: 6px; z-index: 40;
}
.search-results a { display: block; padding: 8px 10px; border-radius: 7px; text-decoration: none; color: var(--ink); font-size: var(--fs-sm); line-height: 1.4; }
.search-results a:hover, .search-results a.active { background: var(--surface-2); }
.search-results a span { display: block; color: var(--muted); font-size: var(--fs-xs); }
.search-results .empty { padding: 10px; color: var(--muted); font-size: var(--fs-sm); }

/* ---------- Shell ---------- */
.shell { display: grid; grid-template-columns: var(--rail) minmax(0, 1fr); min-height: calc(100vh - var(--head)); }
.rail {
  position: sticky; top: calc(var(--head) + env(safe-area-inset-top, 0px));
  height: calc(100vh - var(--head) - env(safe-area-inset-top, 0px));
  overflow-y: auto; border-right: 1px solid var(--rule);
  padding-block: 18px 40px; padding-inline: 14px;
  background: var(--bg);
}
.rail-group { display: grid; gap: 2px; margin-bottom: 18px; }
.rail-label {
  font-family: var(--f-mono); font-size: 0.7rem; text-transform: uppercase; letter-spacing: 0.12em;
  color: var(--muted); padding: 4px 10px 6px;
}
.rail a {
  display: grid; grid-template-columns: 30px 1fr auto; align-items: baseline; gap: 4px;
  padding: 6px 10px; border-radius: 8px; text-decoration: none; color: var(--ink-2);
  font-size: var(--fs-sm); line-height: 1.35;
}
.rail a .n { font-family: var(--f-mono); font-size: 0.75rem; color: var(--muted); }
.rail a:hover { background: var(--surface-2); color: var(--ink); }
.rail a[aria-current="page"] { background: var(--ink); color: var(--bg); }
.rail a[aria-current="page"] .n { color: var(--bg); opacity: 0.7; }
.rail a .done { width: 16px; height: 16px; border-radius: 50%; background: var(--ok); color: var(--bg); display: inline-grid; place-items: center; font-size: 10px; align-self: center; }
.rail a.solo { grid-template-columns: 30px 1fr; }
.rail-progress { margin: 4px 10px 20px; }
.rail-progress .bar { height: 6px; background: var(--surface-2); border-radius: 99px; overflow: hidden; }
.rail-progress .bar i { display: block; height: 100%; background: var(--accent); border-radius: 99px; transition: width 0.4s ease; }
.rail-progress .lbl { display: flex; justify-content: space-between; font-size: var(--fs-xs); color: var(--muted); margin-top: 6px; font-variant-numeric: tabular-nums; }

main { min-width: 0; padding-block: 28px 80px; padding-inline: clamp(16px, 4vw, 56px); }
.page { max-width: 860px; margin-inline: auto; display: grid; gap: 28px; }
.page.wide { max-width: 1080px; }

/* ---------- Home ---------- */
.hero {
  position: relative; overflow: hidden;
  border: 1px solid var(--rule); border-radius: 16px;
  background:
    linear-gradient(var(--grid) 1px, transparent 1px) 0 0 / 24px 24px,
    linear-gradient(90deg, var(--grid) 1px, transparent 1px) 0 0 / 24px 24px,
    var(--surface);
  padding: clamp(24px, 5vw, 52px);
  display: grid; grid-template-columns: minmax(0, 1.25fr) minmax(0, 1fr); gap: 32px; align-items: center;
}
.eyebrow { font-family: var(--f-mono); font-size: 0.75rem; letter-spacing: 0.12em; text-transform: uppercase; color: var(--accent); }
.hero h1 { font-size: var(--fs-3xl); font-weight: 800; letter-spacing: -0.035em; margin-top: 10px; }
.hero h1 em { font-style: normal; color: var(--accent); }
.hero p.lead { font-size: var(--fs-lg); color: var(--ink-2); margin-top: 16px; max-width: 34em; line-height: 1.55; }
.hero .actions { display: flex; flex-wrap: wrap; gap: 10px; margin-top: 26px; }
.btn {
  display: inline-flex; align-items: center; gap: 8px; height: 44px; padding-inline: 18px;
  border-radius: 9px; border: 1px solid var(--ink); background: var(--ink); color: var(--bg);
  font-weight: 600; text-decoration: none; cursor: pointer; font-size: var(--fs-sm);
}
.btn:hover { background: var(--accent); border-color: var(--accent); color: var(--accent-ink); }
.btn.ghost { background: transparent; color: var(--ink); border-color: var(--rule); }
.btn.ghost:hover { border-color: var(--ink); background: transparent; color: var(--ink); }
.btn.small { height: 36px; padding-inline: 14px; }
.tensor-visual { width: 100%; max-width: 380px; justify-self: center; }
.tensor-visual .cell { fill: var(--fig-n); stroke: var(--rule); }
.tensor-visual .cell.hot { fill: var(--accent); }
.tensor-visual .cell.warm { fill: var(--fig-a); }
.tensor-visual .cell.cool { fill: var(--fig-s); }
.tensor-visual text { font-family: var(--f-mono); font-size: 11px; fill: var(--muted); }
@media (prefers-reduced-motion: no-preference) {
  .tensor-visual .cell.pulse { animation: pulse 3.2s ease-in-out infinite; }
}
@keyframes pulse { 0%, 100% { opacity: 1; } 50% { opacity: 0.35; } }

.stat-row { display: grid; grid-template-columns: repeat(5, minmax(0, 1fr)); gap: 12px; }
.stat { border: 1px solid var(--rule); border-radius: 12px; padding: 16px 18px; background: var(--surface); }
.stat b { display: block; font-family: var(--f-display); font-size: var(--fs-2xl); font-weight: 800; letter-spacing: -0.03em; font-variant-numeric: tabular-nums; }
.stat span { color: var(--muted); font-size: var(--fs-sm); }

.section-head { display: grid; gap: 6px; }
.section-head h2 { font-size: var(--fs-xl); font-weight: 700; }
.section-head p { color: var(--ink-2); }

.parts { display: grid; gap: 14px; }
.part-card {
  border: 1px solid var(--rule); border-radius: 14px; background: var(--surface);
  display: grid; grid-template-columns: 120px minmax(0, 1fr); overflow: hidden;
}
.part-card .pn {
  background: var(--surface-2); padding: 18px; display: grid; align-content: space-between; gap: 10px;
  border-right: 1px solid var(--rule);
}
.part-card .pn b { font-family: var(--f-display); font-size: 2.6rem; font-weight: 800; line-height: 1; letter-spacing: -0.04em; color: var(--accent); }
.part-card .pn span { font-family: var(--f-mono); font-size: 0.7rem; letter-spacing: 0.1em; text-transform: uppercase; color: var(--muted); }
.part-card .pb { padding: 18px 20px; display: grid; gap: 10px; min-width: 0; }
.part-card h3 { font-size: var(--fs-lg); }
.part-card p { color: var(--ink-2); font-size: var(--fs-sm); }
.chip-row { display: flex; flex-wrap: wrap; gap: 6px; }
.chip {
  display: inline-flex; align-items: center; gap: 6px; padding: 4px 10px; border-radius: 99px;
  border: 1px solid var(--rule); background: var(--bg); color: var(--ink-2);
  font-size: var(--fs-xs); text-decoration: none; line-height: 1.4;
}
a.chip:hover { border-color: var(--accent); color: var(--accent); }
.chip .k { font-family: var(--f-mono); color: var(--muted); }
.chip.ok { border-color: var(--ok); color: var(--ok); }

.steps { display: grid; grid-template-columns: repeat(4, minmax(0, 1fr)); gap: 12px; counter-reset: step; }
.step { border-top: 3px solid var(--ink); padding-top: 12px; display: grid; gap: 6px; }
.step b { font-family: var(--f-display); font-size: var(--fs-md); }
.step span { color: var(--ink-2); font-size: var(--fs-sm); }
.step .k { font-family: var(--f-mono); font-size: 0.72rem; color: var(--accent); letter-spacing: 0.08em; }

/* ---------- Chapter ---------- */
.ch-head { display: grid; gap: 14px; padding-bottom: 24px; border-bottom: 1px solid var(--rule); }
.ch-meta { display: flex; flex-wrap: wrap; gap: 8px 16px; align-items: center; font-family: var(--f-mono); font-size: 0.75rem; color: var(--muted); letter-spacing: 0.04em; }
.ch-meta .part { color: var(--accent); text-transform: uppercase; letter-spacing: 0.12em; }
.ch-head h1 { font-size: var(--fs-2xl); font-weight: 800; letter-spacing: -0.03em; }
.ch-head h1 .num { color: var(--accent); margin-right: 0.3em; }
.ch-head .intro { font-size: var(--fs-lg); color: var(--ink-2); line-height: 1.55; }
.signature {
  display: inline-flex; align-self: start; max-width: 100%; overflow-x: auto;
  font-family: var(--f-mono); font-size: 0.82rem; padding: 7px 12px; border-radius: 8px;
  background: var(--code-bg); color: var(--code-fg); white-space: nowrap;
}
.signature .p { color: var(--tk-kw); margin-right: 8px; user-select: none; }

.goals { border: 1px solid var(--rule); border-radius: 12px; background: var(--surface); padding: 18px 20px; display: grid; gap: 10px; }
.goals h3 { font-size: var(--fs-sm); font-family: var(--f-mono); text-transform: uppercase; letter-spacing: 0.1em; color: var(--muted); font-weight: 600; }
.goals ul { margin: 0; padding-left: 0; list-style: none; display: grid; gap: 6px; }
.goals li { display: grid; grid-template-columns: 22px 1fr; color: var(--ink-2); font-size: var(--fs-sm); }
.goals li::before { content: "→"; color: var(--accent); font-family: var(--f-mono); }

.toc { display: flex; flex-wrap: wrap; gap: 6px; }
.toc button { border: 1px solid var(--rule); background: var(--surface); border-radius: 99px; padding: 5px 12px; font-size: var(--fs-xs); cursor: pointer; color: var(--ink-2); }
.toc button:hover { border-color: var(--ink); color: var(--ink); }
.toc button .k { font-family: var(--f-mono); color: var(--accent); margin-right: 6px; }

.sec { display: grid; gap: 18px; scroll-margin-top: calc(var(--head) + 20px); }
.sec > h2 { font-size: var(--fs-xl); font-weight: 700; display: grid; grid-template-columns: auto 1fr; gap: 12px; align-items: baseline; padding-top: 10px; }
.sec > h2 .k { font-family: var(--f-mono); font-size: 0.85rem; color: var(--accent); font-weight: 600; }
.sec h3 { font-size: var(--fs-lg); font-weight: 700; margin-top: 6px; }
.prose { display: grid; gap: 14px; max-width: 70ch; }
.prose p, .prose li { color: var(--ink); }
.prose ul, .prose ol { margin: 0; padding-left: 1.3em; display: grid; gap: 6px; }
.prose b, .prose strong { font-weight: 600; }
.prose .term { font-weight: 600; color: var(--ink); border-bottom: 1px dashed var(--muted); }

.callout { border-radius: 10px; padding: 14px 16px; display: grid; grid-template-columns: 28px minmax(0, 1fr); gap: 8px; font-size: var(--fs-sm); line-height: 1.6; max-width: 76ch; }
.callout .ic { font-family: var(--f-mono); font-weight: 700; font-size: 0.9rem; width: 24px; height: 24px; border-radius: 6px; display: grid; place-items: center; }
.callout.tip { background: var(--signal-soft); }
.callout.tip .ic { background: var(--signal); color: var(--bg); }
.callout.warn { background: var(--warn-soft); }
.callout.warn .ic { background: var(--warn); color: var(--bg); }
.callout.job { background: var(--accent-soft); }
.callout.job .ic { background: var(--accent); color: var(--accent-ink); }
.callout b.t { display: block; margin-bottom: 2px; }

.formula {
  border: 1px solid var(--rule); border-left: 3px solid var(--accent); border-radius: 0 10px 10px 0;
  background: var(--surface); padding: 14px 18px; overflow-x: auto; display: grid; gap: 6px; max-width: 76ch;
}
.formula .f { font-family: "Cambria Math", "STIX Two Math", "Times New Roman", serif; font-size: 1.22rem; white-space: nowrap; color: var(--ink); }
.formula .f sub, .formula .f sup { font-size: 0.7em; }
.formula .note { font-size: var(--fs-sm); color: var(--muted); }
.formula { overflow-x: visible; min-width: 0; }
.formula .f { overflow-x: auto; max-width: 100%; padding-bottom: 2px; }
.formula .fvars { border-top: 1px dashed var(--rule); padding-top: 8px; margin-top: 2px; }
.formula .fvars summary { cursor: pointer; font-family: var(--f-mono); font-size: 0.72rem; text-transform: uppercase; letter-spacing: 0.08em; color: var(--accent); }
.formula dl { display: grid; grid-template-columns: max-content minmax(0, 1fr); gap: 6px 16px; margin: 10px 0 4px; font-size: var(--fs-sm); }
.formula dt { font-family: "Cambria Math", "STIX Two Math", "Times New Roman", serif; font-size: 1.05rem; color: var(--ink); white-space: nowrap; }
.formula dd { margin: 0; color: var(--ink-2); line-height: 1.5; }
.formula .fex { display: grid; gap: 2px; margin-top: 8px; padding: 10px 12px; border-radius: 8px; background: var(--signal-soft); font-size: var(--fs-sm); line-height: 1.55; }
.formula .fex b { font-family: var(--f-mono); font-size: 0.72rem; text-transform: uppercase; letter-spacing: 0.08em; color: var(--signal); }
.plate.result { border-color: var(--ok); position: relative; }
.plate.result figcaption b { color: var(--ok); }
.res-badge { position: absolute; top: 10px; right: 12px; z-index: 1; font-family: var(--f-mono); font-size: 0.66rem; letter-spacing: 0.1em; text-transform: uppercase; color: var(--ok); background: var(--ok-soft); padding: 3px 8px; border-radius: 99px; }
.plate.result .fig-scroll { padding-top: 30px; }
.res-body { padding: 34px 16px 12px; display: grid; gap: 10px; overflow-x: auto; }
.res-body .fig-scroll { padding: 0; }
.res-list { display: grid; gap: 8px; }
.res-row { display: grid; grid-template-columns: 110px minmax(0, 1fr); gap: 12px; align-items: start; font-size: var(--fs-sm); }
.res-row .chip { justify-content: center; font-family: var(--f-mono); }
.res-row p { margin: 0; line-height: 1.55; overflow-wrap: anywhere; }
.res-row p.pre { white-space: pre-wrap; font-family: var(--f-mono); font-size: 0.8rem; }
.res-row code.good { color: var(--ok); }
.res-row code.bad { color: var(--bad); }
.tok-row code { margin: 2px 0; display: inline-block; }
@media (max-width: 640px) { .res-row { grid-template-columns: minmax(0, 1fr); gap: 4px; } .res-row .chip { justify-self: start; } .formula dl { grid-template-columns: minmax(0, 1fr); gap: 2px; } .formula dd { margin-bottom: 6px; } }
.frac { display: inline-flex; flex-direction: column; vertical-align: middle; text-align: center; margin: 0 2px; }
.frac > span:first-child { border-bottom: 1px solid currentColor; padding: 0 3px; }
.frac > span { line-height: 1.2; font-size: 0.92em; }

.code-block { border-radius: 10px; background: var(--code-bg); overflow: hidden; border: 1px solid var(--code-rule); max-width: 100%; }
.code-head { display: flex; align-items: center; justify-content: space-between; gap: 10px; padding: 8px 12px; border-bottom: 1px solid var(--code-rule); font-family: var(--f-mono); font-size: 0.75rem; color: var(--tk-com); }
.code-head .dots { display: inline-flex; gap: 6px; margin-right: 10px; }
.code-head .dots i { width: 9px; height: 9px; border-radius: 50%; background: var(--code-rule); display: block; }
.code-head .ttl { display: inline-flex; align-items: center; min-width: 0; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.copy-btn { border: 1px solid var(--code-rule); background: transparent; color: var(--code-fg); border-radius: 6px; padding: 3px 9px; font-family: var(--f-mono); font-size: 0.72rem; cursor: pointer; flex: none; }
.copy-btn:hover { border-color: var(--tk-com); }
.code-block pre, .signature, code { font-variant-ligatures: none; }
.code-block pre { margin: 0; padding: 14px 16px; overflow-x: auto; font-family: var(--f-mono); font-size: 0.84rem; line-height: 1.65; color: var(--code-fg); tab-size: 4; }
.code-block code { background: none; padding: 0; font-size: inherit; color: inherit; border-radius: 0; }
.code-out { border-top: 1px dashed var(--code-rule); padding: 10px 16px 12px; font-family: var(--f-mono); font-size: 0.8rem; color: var(--tk-str); white-space: pre-wrap; }
.code-out::before { content: "▸ output"; display: block; color: var(--tk-com); font-size: 0.7rem; margin-bottom: 4px; letter-spacing: 0.06em; }
.token.comment, .token.prolog { color: var(--tk-com); font-style: italic; }
.token.keyword, .token.boolean, .token.builtin { color: var(--tk-kw); }
.token.string, .token.triple-quoted-string { color: var(--tk-str); }
.token.number { color: var(--tk-num); }
.token.function, .token.class-name, .token.decorator { color: var(--tk-fn); }
.token.operator, .token.punctuation { color: var(--tk-op); }

.plate {
  border: 1px solid var(--rule); border-radius: 12px; overflow: hidden;
  background:
    linear-gradient(var(--grid) 1px, transparent 1px) 0 0 / 20px 20px,
    linear-gradient(90deg, var(--grid) 1px, transparent 1px) 0 0 / 20px 20px,
    var(--surface);
}
.plate .fig-scroll { overflow-x: auto; padding: 18px 14px 10px; }
.plate .fig-scroll svg { display: block; width: 100%; min-width: 560px; height: auto; margin-inline: auto; }
.plate figcaption { padding: 10px 16px 14px; font-size: var(--fs-sm); color: var(--ink-2); border-top: 1px solid var(--rule); background: var(--surface); }
.plate figcaption b { font-family: var(--f-mono); font-size: 0.75rem; color: var(--accent); margin-right: 8px; letter-spacing: 0.05em; }
figure { margin: 0; }

/* SVG figure classes */
.fig text { font-family: var(--f-body); fill: var(--fig-text); font-size: 13px; white-space: pre; }
.fig .mono { font-family: var(--f-mono); font-size: 12px; }
.fig .small { font-size: 11px; }
.fig .muted { fill: var(--muted); }
.fig .bold { font-weight: 600; }
.fig .ttl { font-family: var(--f-display); font-weight: 700; font-size: 14px; }
.fig .acc-t { fill: var(--accent); }
.fig .sig-t { fill: var(--signal); }
.fig .ok-t { fill: var(--ok); }
.fig .bad-t { fill: var(--bad); }
.fig .ln { stroke: var(--fig-line); stroke-width: 1.4; fill: none; }
.fig .ln-thin { stroke: var(--fig-line); stroke-width: 1; fill: none; opacity: 0.6; }
.fig .ln-acc { stroke: var(--accent); stroke-width: 2.2; fill: none; }
.fig .ln-sig { stroke: var(--signal); stroke-width: 2.2; fill: none; }
.fig .ln-ok { stroke: var(--ok); stroke-width: 2.2; fill: none; }
.fig .ln-bad { stroke: var(--bad); stroke-width: 2.2; fill: none; }
.fig .ln-muted { stroke: var(--muted); stroke-width: 1.4; fill: none; }
.fig .dash { stroke-dasharray: 5 4; }
.fig .b { fill: var(--fig-box); stroke: var(--fig-line); stroke-width: 1.3; }
.fig .b-a { fill: var(--fig-a); stroke: var(--accent); stroke-width: 1.3; }
.fig .b-s { fill: var(--fig-s); stroke: var(--signal); stroke-width: 1.3; }
.fig .b-n { fill: var(--fig-n); stroke: var(--fig-line); stroke-width: 1; }
.fig .b-ok { fill: var(--fig-ok); stroke: var(--ok); stroke-width: 1.3; }
.fig .b-solid { fill: var(--accent); stroke: var(--accent); }
.fig .b-ink { fill: var(--fig-text); stroke: var(--fig-text); }
.fig .inv { fill: var(--fig-box); }
.fig .dot { fill: var(--fig-line); }
.fig .dot-a { fill: var(--accent); }
.fig .dot-s { fill: var(--signal); }
.fig .dot-ok { fill: var(--ok); }
.fig .area-a { fill: var(--accent); opacity: 0.12; }
.fig .area-s { fill: var(--signal); opacity: 0.12; }
.fig .ah { fill: var(--fig-line); }
.fig .ah-a { fill: var(--accent); }
.fig .ah-s { fill: var(--signal); }
.fig .ah-ok { fill: var(--ok); }
.fig .grid-ln { stroke: var(--rule); stroke-width: 1; }

/* ---------- Widgets ---------- */
.widget { border: 1px solid var(--ink); border-radius: 12px; background: var(--surface); padding: 18px; display: grid; gap: 14px; }
.widget-head { display: flex; flex-wrap: wrap; justify-content: space-between; gap: 8px; align-items: baseline; }
.widget-head b { font-family: var(--f-display); font-size: var(--fs-md); }
.widget-head span { font-family: var(--f-mono); font-size: 0.7rem; letter-spacing: 0.1em; text-transform: uppercase; color: var(--accent); }
.widget p.hint { font-size: var(--fs-sm); color: var(--ink-2); }
.controls { display: flex; flex-wrap: wrap; gap: 14px 22px; align-items: center; }
.control { display: grid; gap: 4px; font-size: var(--fs-sm); min-width: 160px; flex: 1; }
.control label { display: flex; justify-content: space-between; gap: 8px; color: var(--ink-2); }
.control label output { font-family: var(--f-mono); color: var(--ink); font-variant-numeric: tabular-nums; }
.control input[type="range"] { width: 100%; accent-color: var(--accent); }
.control input[type="number"], .control select {
  height: 36px; border: 1px solid var(--rule); border-radius: 8px; background: var(--bg); color: var(--ink); padding: 0 10px; font: inherit; font-family: var(--f-mono); font-size: var(--fs-sm);
}
.seg { display: inline-flex; flex-wrap: wrap; border: 1px solid var(--rule); border-radius: 8px; overflow: hidden; }
.seg button { border: 0; background: var(--bg); padding: 7px 12px; cursor: pointer; font-size: var(--fs-xs); font-family: var(--f-mono); color: var(--ink-2); border-right: 1px solid var(--rule); }
.seg button:last-child { border-right: 0; }
.seg button[aria-pressed="true"] { background: var(--ink); color: var(--bg); }
.widget-out { overflow-x: auto; }
.widget-out svg { display: block; width: 100%; min-width: 520px; height: auto; }
.readout { display: flex; flex-wrap: wrap; gap: 8px; }
.readout .chip { font-family: var(--f-mono); font-variant-numeric: tabular-nums; }
.calc-result { font-family: var(--f-mono); font-size: var(--fs-lg); padding: 12px 14px; background: var(--code-bg); color: var(--code-fg); border-radius: 8px; overflow-x: auto; white-space: nowrap; }
.calc-result .hl { color: var(--tk-num); font-weight: 600; }

/* ---------- Tables ---------- */
.table-wrap { overflow-x: auto; border: 1px solid var(--rule); border-radius: 10px; background: var(--surface); }
table { border-collapse: collapse; width: 100%; font-size: var(--fs-sm); }
th, td { text-align: left; padding: 10px 14px; border-bottom: 1px solid var(--rule); vertical-align: top; }
th { font-family: var(--f-mono); font-size: 0.72rem; text-transform: uppercase; letter-spacing: 0.08em; color: var(--muted); font-weight: 600; background: var(--surface-2); white-space: nowrap; }
tr:last-child td { border-bottom: 0; }
td code { white-space: nowrap; }

.cards { display: grid; grid-template-columns: repeat(auto-fit, minmax(210px, 1fr)); gap: 12px; }
.card { border: 1px solid var(--rule); border-radius: 12px; padding: 16px; background: var(--surface); display: grid; gap: 6px; align-content: start; }
.card b { font-family: var(--f-display); font-size: var(--fs-md); }
.card .k { font-family: var(--f-mono); font-size: 0.7rem; color: var(--accent); letter-spacing: 0.1em; text-transform: uppercase; }
.card p { font-size: var(--fs-sm); color: var(--ink-2); }

/* ---------- Summary / interview ---------- */
.summary { border-radius: 14px; background: var(--ink); color: var(--bg); padding: 22px 24px; display: grid; gap: 12px; }
.summary h2 { font-size: var(--fs-lg); }
.summary ul { margin: 0; padding-left: 0; list-style: none; display: grid; gap: 8px; }
.summary li { display: grid; grid-template-columns: 26px 1fr; font-size: var(--fs-sm); line-height: 1.55; }
.summary li::before { content: "✓"; color: var(--accent); font-weight: 700; }
.summary code { background: rgba(127, 127, 127, 0.25); color: inherit; }

details.qa { border: 1px solid var(--rule); border-radius: 10px; background: var(--surface); }
details.qa + details.qa { margin-top: 8px; }
details.qa summary { cursor: pointer; padding: 13px 16px; font-weight: 600; font-size: var(--fs-sm); list-style: none; display: grid; grid-template-columns: 1fr auto; gap: 12px; }
details.qa summary::-webkit-details-marker { display: none; }
details.qa summary::after { content: "+"; font-family: var(--f-mono); color: var(--accent); font-size: 1.1rem; line-height: 1; }
details.qa[open] summary::after { content: "−"; }
details.qa .ans { padding: 0 16px 14px; color: var(--ink-2); font-size: var(--fs-sm); display: grid; gap: 8px; }

/* ---------- Quiz ---------- */
.quiz { border: 2px solid var(--ink); border-radius: 16px; background: var(--surface); overflow: hidden; }
.quiz-head { padding: 18px 22px; background: var(--ink); color: var(--bg); display: flex; flex-wrap: wrap; justify-content: space-between; gap: 10px; align-items: center; }
.quiz-head h2 { font-size: var(--fs-lg); }
.quiz-head .score { font-family: var(--f-mono); font-size: var(--fs-sm); font-variant-numeric: tabular-nums; }
.quiz-body { padding: 8px 22px 22px; display: grid; }
.q { padding-block: 18px; border-bottom: 1px solid var(--rule); display: grid; gap: 10px; }
.q:last-of-type { border-bottom: 0; }
.q-title { display: grid; grid-template-columns: 34px minmax(0, 1fr); font-weight: 600; }
.q-title .n { font-family: var(--f-mono); color: var(--accent); font-size: var(--fs-sm); padding-top: 2px; }
.q-title > div { min-width: 0; }
.opts { display: grid; gap: 8px; padding-left: 34px; }
.opt {
  display: grid; grid-template-columns: 28px minmax(0, 1fr); gap: 6px; align-items: start; text-align: left;
  border: 1px solid var(--rule); border-radius: 9px; background: var(--bg); padding: 10px 12px; cursor: pointer; font-size: var(--fs-sm); line-height: 1.5;
}
.opt:hover:not([disabled]) { border-color: var(--ink); }
.opt .l { font-family: var(--f-mono); font-weight: 600; color: var(--muted); }
.opt[disabled] { cursor: default; }
.opt.correct { border-color: var(--ok); background: var(--ok-soft); }
.opt.correct .l { color: var(--ok); }
.opt.wrong { border-color: var(--bad); background: var(--bad-soft); }
.opt.wrong .l { color: var(--bad); }
.explain { margin-left: 34px; font-size: var(--fs-sm); color: var(--ink-2); padding: 10px 12px; border-left: 3px solid var(--signal); background: var(--signal-soft); border-radius: 0 8px 8px 0; }
.explain b { color: var(--ink); }
.quiz-foot { display: flex; flex-wrap: wrap; gap: 12px; align-items: center; justify-content: space-between; padding-top: 18px; }
.result-banner { padding: 16px 18px; border-radius: 10px; background: var(--surface-2); display: grid; gap: 4px; }
.result-banner b { font-family: var(--f-display); font-size: var(--fs-xl); font-variant-numeric: tabular-nums; }
.result-banner.good { background: var(--ok-soft); }
.result-banner.mid { background: var(--warn-soft); }
.result-banner.low { background: var(--bad-soft); }

.pager { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; }
.pager a { border: 1px solid var(--rule); border-radius: 12px; padding: 14px 16px; text-decoration: none; color: var(--ink); display: grid; gap: 2px; background: var(--surface); }
.pager a:hover { border-color: var(--ink); }
.pager a span { font-family: var(--f-mono); font-size: 0.72rem; color: var(--muted); letter-spacing: 0.06em; }
.pager a b { font-family: var(--f-display); font-size: var(--fs-md); }
.pager a.next { text-align: right; }

/* ---------- Practice tasks ---------- */
.tasks { display: grid; gap: 12px; }
.task { border: 1px solid var(--rule); border-radius: 12px; background: var(--surface); padding: 16px 18px; display: grid; gap: 10px; min-width: 0; }
.task-head { display: flex; flex-wrap: wrap; align-items: baseline; gap: 8px 12px; }
.task-head b { font-family: var(--f-display); font-size: var(--fs-md); flex: 1; min-width: 180px; }
.task-n { font-family: var(--f-mono); font-size: 0.8rem; color: var(--accent); }
.task > p { font-size: var(--fs-sm); color: var(--ink-2); max-width: 76ch; }
.task details.qa { background: var(--bg); }
.task details.qa .ans { padding: 0 12px 12px; }
.chip.lvl-1 { border-color: var(--ok); color: var(--ok); }
.chip.lvl-2 { border-color: var(--warn); color: var(--warn); }
.chip.lvl-3 { border-color: var(--bad); color: var(--bad); }

/* ---------- Cheat sheet ---------- */
.cheat-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(min(100%, 640px), 1fr)); gap: 18px; align-items: start; }
.cheat { display: grid; gap: 8px; min-width: 0; }
.cheat-head { display: flex; justify-content: space-between; align-items: center; gap: 10px; }
.cheat-head h3 { font-size: var(--fs-md); }
.cheat .code-block pre { font-size: 0.78rem; }
code.err { white-space: normal; word-break: break-word; color: var(--bad); }

/* ---------- Glossary / career ---------- */
.gloss-tools { display: flex; flex-wrap: wrap; gap: 10px; align-items: center; }
.gloss-tools input { flex: 1; min-width: 200px; height: 42px; border: 1px solid var(--rule); border-radius: 9px; background: var(--surface); color: var(--ink); padding: 0 14px; font: inherit; }
.gloss { display: grid; grid-template-columns: repeat(auto-fill, minmax(260px, 1fr)); gap: 10px; }
.gterm { border: 1px solid var(--rule); border-radius: 10px; padding: 14px; background: var(--surface); display: grid; gap: 4px; align-content: start; }
.gterm b { font-family: var(--f-display); }
.gterm .tr { font-family: var(--f-mono); font-size: var(--fs-xs); color: var(--accent); }
.gterm p { font-size: var(--fs-sm); color: var(--ink-2); }
.gterm a { font-size: var(--fs-xs); }

.road { display: grid; gap: 0; position: relative; }
.road-step { display: grid; grid-template-columns: 56px minmax(0, 1fr); gap: 14px; position: relative; padding-bottom: 22px; }
.road-step::before { content: ""; position: absolute; left: 27px; top: 44px; bottom: 0; width: 2px; background: var(--rule); }
.road-step:last-child::before { display: none; }
.road-step .badge { width: 56px; height: 44px; border-radius: 10px; background: var(--ink); color: var(--bg); display: grid; place-items: center; font-family: var(--f-mono); font-size: 0.8rem; font-weight: 600; }
.road-step .body { border: 1px solid var(--rule); border-radius: 12px; background: var(--surface); padding: 14px 16px; display: grid; gap: 8px; }
.road-step h3 { font-size: var(--fs-md); }
.road-step p { font-size: var(--fs-sm); color: var(--ink-2); }

.check-list { list-style: none; margin: 0; padding: 0; display: grid; gap: 6px; }
.check-list label { display: grid; grid-template-columns: 24px 1fr; gap: 6px; align-items: start; font-size: var(--fs-sm); cursor: pointer; }
.check-list input { accent-color: var(--ok); width: 16px; height: 16px; margin-top: 4px; }

footer.site-foot { border-top: 1px solid var(--rule); margin-top: 40px; padding-top: 18px; font-size: var(--fs-xs); color: var(--muted); display: grid; gap: 6px; max-width: 860px; margin-inline: auto; }

.scrim { display: none; }

/* ---------- Responsive ---------- */
@media (max-width: 1060px) {
  .search-box { width: min(220px, 30vw); }
}
@media (max-width: 920px) {
  .shell { grid-template-columns: minmax(0, 1fr); }
  .menu-btn { display: inline-flex; }
  .rail {
    position: fixed; z-index: 50; left: 0; top: 0; bottom: 0; width: min(320px, 86vw);
    height: 100%; padding-top: calc(18px + env(safe-area-inset-top, 0px));
    transform: translateX(-102%); transition: transform 0.25s ease; box-shadow: var(--shadow);
  }
  body.nav-open .rail { transform: none; }
  body.nav-open .scrim { display: block; position: fixed; inset: 0; z-index: 45; background: rgba(0, 0, 0, 0.35); }
  .hero { grid-template-columns: minmax(0, 1fr); }
  .tensor-visual { max-width: 300px; }
  .stat-row { grid-template-columns: repeat(3, minmax(0, 1fr)); }
  .steps { grid-template-columns: repeat(2, minmax(0, 1fr)); }
}
@media (max-width: 640px) {
  .brand small { display: none; }
  .search-box { display: none; }
  .part-card { grid-template-columns: minmax(0, 1fr); }
  .stat-row { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .part-card .pn { border-right: 0; border-bottom: 1px solid var(--rule); grid-template-columns: auto 1fr; align-items: center; display: flex; gap: 14px; }
  .pager { grid-template-columns: minmax(0, 1fr); }
  .pager a.next { text-align: left; }
  .opts, .explain { padding-left: 0; margin-left: 0; }
  .quiz-body { padding-inline: 16px; }
  .ch-head h1 { font-size: var(--fs-xl); }
}
@media (max-width: 420px) {
  .steps { grid-template-columns: minmax(0, 1fr); }
  .topbar { gap: 8px; }
  .brand span.name { font-size: 1rem; }
}
@media (prefers-reduced-motion: reduce) {
  * { scroll-behavior: auto !important; transition: none !important; animation: none !important; }
}