/* Reader styles shared by the language guides. Extracted from the C++ guide (guide/index.html).
   Per-guide chapter routing rules are generated by build.mjs. */
[hidden]{display:none!important}
/* Layout: docs reader. Left chapter rail, centred ~70ch reading column, right "on this page" rail on wide screens.
   Identity: cool lab-notebook paper, navy ink, one cobalt accent; amber = interview traps, teal = key results. */
:root {
  --bg: #f4f6f9;
  --surface: #ffffff;
  --surface-2: #eaedf3;
  --ink: #141a26;
  --ink-2: #4a5366;
  --ink-3: #7a8396;
  --rule: #d7dce6;
  --accent: #2b47d4;
  --accent-ink: #ffffff;
  --accent-soft: #e2e7fc;
  --trap: #a8500c;
  --trap-soft: #fbefe2;
  --key: #0b7560;
  --key-soft: #dcf1ea;
  --rs: #7f3aae;
  --rs-soft: #f1e6f8;
  --code-bg: #eef1f6;
  --hl-kw: #7f3aae;
  --hl-str: #0b7560;
  --hl-num: #a8500c;
  --hl-com: #7a8396;
  --hl-fn: #2b47d4;
  --shadow: 0 1px 2px rgba(20, 26, 38, .06), 0 8px 24px rgba(20, 26, 38, .06);

  --f-display: "Bricolage Grotesque", "Avenir Next", "Segoe UI", system-ui, sans-serif;
  --f-body: "Source Serif 4", "Iowan Old Style", Georgia, serif;
  --f-mono: "JetBrains Mono", ui-monospace, "SF Mono", Menlo, Consolas, monospace;

  --rail: 270px;
  --toc: 230px;
  --measure: 72ch;
  --top: 56px;
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #0e121a; --surface: #151a24; --surface-2: #1d2330; --ink: #e5e8ef; --ink-2: #a5adbe; --ink-3: #747d90;
    --rule: #283041; --accent: #8fa3ff; --accent-ink: #0e121a; --accent-soft: #1d2647; --trap: #f2a65e; --trap-soft: #2c2016;
    --key: #52d2b2; --key-soft: #11291f; --rs: #cf9bf2; --rs-soft: #2a1d36; --code-bg: #121722;
    --hl-kw: #cf9bf2; --hl-str: #52d2b2; --hl-num: #f2a65e; --hl-com: #747d90; --hl-fn: #8fa3ff;
    --shadow: 0 1px 2px rgba(0,0,0,.3), 0 8px 24px rgba(0,0,0,.25);
    color-scheme: dark;
  }
}
:root[data-theme="dark"] {
  --bg: #0e121a; --surface: #151a24; --surface-2: #1d2330; --ink: #e5e8ef; --ink-2: #a5adbe; --ink-3: #747d90;
  --rule: #283041; --accent: #8fa3ff; --accent-ink: #0e121a; --accent-soft: #1d2647; --trap: #f2a65e; --trap-soft: #2c2016;
  --key: #52d2b2; --key-soft: #11291f; --rs: #cf9bf2; --rs-soft: #2a1d36; --code-bg: #121722;
  --hl-kw: #cf9bf2; --hl-str: #52d2b2; --hl-num: #f2a65e; --hl-com: #747d90; --hl-fn: #8fa3ff;
  --shadow: 0 1px 2px rgba(0,0,0,.3), 0 8px 24px rgba(0,0,0,.25);
  color-scheme: dark;
}

* { box-sizing: border-box; }
[hidden] { display: none !important; }
html { scroll-padding-top: calc(var(--top) + 16px); }
body {
  background: var(--bg); color: var(--ink);
  font-family: var(--f-body); font-size: 17px; line-height: 1.62;
  -webkit-font-smoothing: antialiased; text-rendering: optimizeLegibility;
}
a { color: var(--accent); text-underline-offset: 2px; text-decoration-thickness: 1px; }
a:hover { text-decoration-thickness: 2px; }
:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; border-radius: 3px; }
@media (prefers-reduced-motion: reduce) { * { transition: none !important; animation: none !important; scroll-behavior: auto !important; } }

/* ---------- top bar ---------- */
.topbar {
  position: sticky; top: env(safe-area-inset-top, 0px); z-index: 30;
  height: var(--top); display: flex; align-items: center; gap: 12px;
  padding-inline: 16px; background: color-mix(in srgb, var(--bg) 88%, transparent);
  backdrop-filter: blur(10px); border-bottom: 1px solid var(--rule);
}
.brand { display: flex; align-items: baseline; gap: 10px; color: var(--ink); text-decoration: none; min-width: 0; }
.brand b { font-family: var(--f-display); font-weight: 700; font-size: 18px; letter-spacing: -.01em; white-space: nowrap; }
.brand .short { display: none; }
.brand > span { font-family: var(--f-mono); font-size: 11px; color: var(--ink-3); white-space: nowrap; }
.topbar .spacer { flex: 1; }
.iconbtn {
  display: inline-flex; align-items: center; justify-content: center; gap: 6px;
  height: 34px; min-width: 34px; padding-inline: 10px; border-radius: 8px;
  border: 1px solid var(--rule); background: var(--surface); color: var(--ink-2);
  font: 500 13px/1 var(--f-display); cursor: pointer;
}
.iconbtn:hover { color: var(--ink); border-color: var(--ink-3); }
.iconbtn svg { width: 16px; height: 16px; }
.searchbtn { min-width: 200px; justify-content: space-between; color: var(--ink-3); }
.searchbtn kbd { font: 11px var(--f-mono); border: 1px solid var(--rule); border-radius: 4px; padding: 1px 5px; }
.menubtn { display: none; }

.roles { display: inline-flex; border: 1px solid var(--rule); border-radius: 8px; overflow: hidden; background: var(--surface); }
.roles button {
  border: 0; background: transparent; color: var(--ink-2); font: 600 12px/1 var(--f-display);
  padding: 0 10px; height: 32px; cursor: pointer; letter-spacing: .02em;
}
.roles button + button { border-left: 1px solid var(--rule); }
.roles button[aria-pressed="true"] { background: var(--accent); color: var(--accent-ink); }

/* ---------- shell ---------- */
.shell { display: grid; grid-template-columns: var(--rail) minmax(0, 1fr); min-height: calc(100vh - var(--top)); }
.rail {
  position: sticky; top: calc(var(--top) + env(safe-area-inset-top, 0px)); align-self: start;
  height: calc(100vh - var(--top)); overflow-y: auto; padding: 20px 12px 40px 16px;
  border-right: 1px solid var(--rule); font-family: var(--f-display);
}
.rail h4 { font: 600 11px/1 var(--f-mono); text-transform: uppercase; letter-spacing: .1em; color: var(--ink-3); margin: 22px 8px 8px; }
.rail h4:first-child { margin-top: 4px; }
.rail a {
  display: grid; grid-template-columns: 26px 1fr auto; align-items: center; gap: 4px;
  padding: 6px 8px; border-radius: 7px; color: var(--ink-2); text-decoration: none; font-size: 14px; line-height: 1.3;
}
.rail a:hover { background: var(--surface-2); color: var(--ink); }
.rail a[aria-current="page"] { background: var(--accent-soft); color: var(--ink); font-weight: 600; }
.rail a .n { font: 500 11px var(--f-mono); color: var(--ink-3); }
.rail .pct { font: 500 10px var(--f-mono); color: var(--ink-3); }
.rail .pct.done { color: var(--key); }

main { min-width: 0; padding: 32px 24px 96px; }
.page { display: grid; grid-template-columns: minmax(0, var(--measure)) var(--toc); gap: 48px; justify-content: center; }
.page > .col { min-width: 0; }
.toc { position: sticky; top: calc(var(--top) + 24px); align-self: start; max-height: calc(100vh - var(--top) - 48px); overflow-y: auto; font-family: var(--f-display); font-size: 13px; }
.toc p { font: 600 11px/1 var(--f-mono); text-transform: uppercase; letter-spacing: .1em; color: var(--ink-3); margin: 0 0 10px; }
.toc a { display: block; padding: 4px 0 4px 12px; border-left: 2px solid var(--rule); color: var(--ink-2); text-decoration: none; line-height: 1.35; }
.toc a.h3 { padding-left: 24px; font-size: 12px; }
.toc a.active { border-left-color: var(--accent); color: var(--ink); }
.toc a.is-done::after { content: " ✓"; color: var(--key); }

@media (max-width: 1240px) { .page { grid-template-columns: minmax(0, var(--measure)); } .toc { display: none; } }
@media (max-width: 900px) {
  .shell { grid-template-columns: minmax(0, 1fr); }
  .rail { position: fixed; inset: var(--top) auto 0 0; width: min(320px, 86vw); z-index: 40; background: var(--bg); transform: translateX(-102%); transition: transform .2s ease; box-shadow: var(--shadow); }
  body.rail-open .rail { transform: none; }
  .menubtn { display: inline-flex; }
  .searchbtn { min-width: 0; }
  .searchbtn .label, .searchbtn kbd, .brand > span { display: none; }
  .topbar { gap: 8px; }
  main { padding: 20px 16px 80px; }
}
@media (max-width: 560px) { .roles button { padding: 0 7px; } .brand .long { display: none; } .brand .short { display: inline; } }

/* ---------- typography ---------- */
h1, h2, h3, h4 { font-family: var(--f-display); color: var(--ink); text-wrap: balance; letter-spacing: -.015em; }
.chapter h1 { font-size: clamp(32px, 5vw, 46px); line-height: 1.05; font-weight: 750; margin: 6px 0 14px; }
.chapter h2 { font-size: 27px; line-height: 1.2; margin: 0 0 14px; font-weight: 700; }
.chapter h3 { font-size: 20px; line-height: 1.3; margin: 32px 0 10px; font-weight: 650; }
.chapter h4 { font-size: 16px; margin: 22px 0 6px; font-weight: 650; }
.chapter p, .chapter li { hyphens: auto; }
.chapter p { margin: 0 0 14px; }
.chapter ul, .chapter ol { padding-left: 1.3em; margin: 0 0 14px; }
.chapter li { margin: 4px 0; }
.chapter strong { font-weight: 650; }
.eyebrow { font: 600 12px/1 var(--f-mono); text-transform: uppercase; letter-spacing: .12em; color: var(--accent); margin: 0; }
.lede { font-size: 20px; line-height: 1.5; color: var(--ink-2); margin: 0 0 16px; }
.ch-meta { display: flex; flex-wrap: wrap; gap: 8px; align-items: center; font: 500 12px var(--f-mono); color: var(--ink-3); }
.ch-head { padding-bottom: 22px; margin-bottom: 30px; border-bottom: 1px solid var(--rule); }

/* sections */
.chapter > section { position: relative; padding-top: 8px; margin-bottom: 44px; }
.sec-head { display: flex; flex-wrap: wrap; gap: 4px 12px; align-items: flex-start; justify-content: space-between; }
.sec-head h2 { flex: 1 1 260px; min-width: 0; overflow-wrap: anywhere; }
.sec-tools { display: flex; flex-wrap: wrap; gap: 6px; align-items: center; padding-top: 6px; flex-shrink: 0; }
.done-toggle {
  display: inline-flex; align-items: center; gap: 6px; height: 26px; padding: 0 9px; border-radius: 999px;
  border: 1px solid var(--rule); background: var(--surface); color: var(--ink-3); font: 500 11px var(--f-mono); cursor: pointer;
}
.done-toggle[aria-pressed="true"] { background: var(--key-soft); border-color: var(--key); color: var(--key); }
section.role-hidden > :not(.sec-head):not(.role-note) { display: none; }
.role-note { display: none; }
section.role-hidden .role-note { display: flex; gap: 10px; align-items: center; font: 13px var(--f-display); color: var(--ink-3); padding: 10px 14px; border: 1px dashed var(--rule); border-radius: 10px; }
.role-note button { border: 0; background: none; color: var(--accent); font: 600 13px var(--f-display); cursor: pointer; padding: 0; }

/* role chips */
.role { display: inline-flex; align-items: center; height: 20px; padding: 0 7px; border-radius: 5px; font: 700 10.5px/1 var(--f-mono); letter-spacing: .05em; }
.role.re { background: var(--accent-soft); color: var(--accent); }
.role.rs { background: var(--rs-soft); color: var(--rs); }
.role.ae { background: var(--key-soft); color: var(--key); }

/* callouts */
.callout { margin: 20px 0; padding: 14px 18px; border-radius: 10px; background: var(--surface); border: 1px solid var(--rule); }
.callout > :last-child { margin-bottom: 0; }
.callout-title { font: 700 12px/1.2 var(--f-mono); text-transform: uppercase; letter-spacing: .08em; margin: 0 0 8px !important; }
.callout.trap { background: var(--trap-soft); border-color: color-mix(in srgb, var(--trap) 35%, transparent); }
.callout.trap .callout-title { color: var(--trap); }
.callout.key { background: var(--key-soft); border-color: color-mix(in srgb, var(--key) 35%, transparent); }
.callout.key .callout-title { color: var(--key); }
.callout.tip .callout-title { color: var(--accent); }
.callout.new { background: var(--rs-soft); border-color: color-mix(in srgb, var(--rs) 35%, transparent); }
.callout.new .callout-title { color: var(--rs); }

/* derivation steps */
.deriv { counter-reset: step; margin: 18px 0; padding: 4px 0 4px 18px; border-left: 2px solid var(--accent); }
.deriv > .step { counter-increment: step; position: relative; margin: 10px 0; }
.deriv > .step::before { content: counter(step); position: absolute; left: -31px; top: 2px; width: 22px; height: 22px; border-radius: 50%; background: var(--accent); color: var(--accent-ink); font: 700 11px/22px var(--f-mono); text-align: center; }
.deriv > .step > :last-child { margin-bottom: 0; }

/* math */
.katex { font-size: 1.06em; }
.katex-display { margin: 16px 0; overflow-x: auto; overflow-y: hidden; padding: 4px 0; }
.math-err { color: var(--trap); font-family: var(--f-mono); font-size: 13px; }

/* code */
code { font-family: var(--f-mono); font-size: .86em; background: var(--code-bg); padding: 1px 5px; border-radius: 4px; }
pre { margin: 16px 0; background: var(--code-bg); border: 1px solid var(--rule); border-radius: 10px; overflow-x: auto; position: relative; }
pre code { display: block; padding: 14px 16px; background: none; font-size: 13.5px; line-height: 1.55; tab-size: 4; }
.copybtn { position: absolute; top: 8px; right: 8px; font: 500 11px var(--f-mono); border: 1px solid var(--rule); background: var(--surface); color: var(--ink-3); border-radius: 6px; padding: 3px 8px; cursor: pointer; opacity: 0; transition: opacity .15s; }
pre:hover .copybtn, .copybtn:focus { opacity: 1; }
.hljs-keyword, .hljs-built_in, .hljs-meta .hljs-keyword { color: var(--hl-kw); }
.hljs-string, .hljs-doctag { color: var(--hl-str); }
.hljs-number, .hljs-literal { color: var(--hl-num); }
.hljs-comment { color: var(--hl-com); font-style: italic; }
.hljs-title, .hljs-title.function_, .hljs-title.class_ { color: var(--hl-fn); }
.hljs-params { color: var(--ink); }

/* tables */
.table-wrap { overflow-x: auto; margin: 18px 0; border: 1px solid var(--rule); border-radius: 10px; background: var(--surface); }
table { border-collapse: collapse; width: 100%; font-size: 14.5px; font-variant-numeric: tabular-nums; }
th, td { text-align: left; padding: 8px 12px; border-bottom: 1px solid var(--rule); vertical-align: top; }
th { font: 600 12px/1.3 var(--f-display); text-transform: uppercase; letter-spacing: .04em; color: var(--ink-2); background: var(--surface-2); }
tr:last-child td { border-bottom: 0; }
td.num, th.num { text-align: right; }

/* figures / svg diagrams */
figure.fig { margin: 24px 0; padding: 18px; background: var(--surface); border: 1px solid var(--rule); border-radius: 12px; color: var(--ink); }
figure.fig .svgwrap { overflow-x: auto; }
figure.fig svg { display: block; max-width: 100%; height: auto; margin: 0 auto; font-family: var(--f-display); }
figure.fig figcaption { font: 14px/1.5 var(--f-display); color: var(--ink-2); margin-top: 12px; }
figure.fig figcaption b { color: var(--ink); }
svg .d-box { fill: var(--surface); stroke: currentColor; stroke-width: 1.4; }
svg .d-soft { fill: var(--surface-2); stroke: var(--rule); stroke-width: 1; }
svg .d-acc { fill: var(--accent-soft); stroke: var(--accent); stroke-width: 1.5; }
svg .d-key { fill: var(--key-soft); stroke: var(--key); stroke-width: 1.5; }
svg .d-trap { fill: var(--trap-soft); stroke: var(--trap); stroke-width: 1.5; }
svg .d-rs { fill: var(--rs-soft); stroke: var(--rs); stroke-width: 1.5; }
svg .d-line { fill: none; stroke: currentColor; stroke-width: 1.4; }
svg .d-line-acc { fill: none; stroke: var(--accent); stroke-width: 1.8; }
svg .d-line-key { fill: none; stroke: var(--key); stroke-width: 1.8; }
svg .d-line-trap { fill: none; stroke: var(--trap); stroke-width: 1.8; }
svg .d-dash { stroke-dasharray: 4 4; }
svg .d-grid { stroke: var(--rule); stroke-width: 1; fill: none; }
svg .d-fill-acc { fill: var(--accent); }
svg .d-fill-key { fill: var(--key); }
svg .d-fill-trap { fill: var(--trap); }
svg .d-fill-rs { fill: var(--rs); }
svg .d-fill-ink { fill: currentColor; }
svg .d-fill-muted { fill: var(--ink-3); }
svg text { fill: currentColor; font-size: 13px; }
svg text.t-muted { fill: var(--ink-2); font-size: 12px; }
svg text.t-small { font-size: 11px; fill: var(--ink-2); }
svg text.t-mono { font-family: var(--f-mono); font-size: 12px; }
svg text.t-bold { font-weight: 700; }
svg text.t-acc { fill: var(--accent); }
svg text.t-key { fill: var(--key); }
svg text.t-trap { fill: var(--trap); }
svg text.t-rs { fill: var(--rs); }

/* Q&A */
.qa details { border: 1px solid var(--rule); border-radius: 10px; background: var(--surface); margin: 10px 0; }
.qa summary { cursor: pointer; list-style: none; padding: 12px 16px 12px 44px; position: relative; font: 500 16px/1.45 var(--f-display); }
.qa summary::-webkit-details-marker { display: none; }
.qa summary::before { content: "+"; position: absolute; left: 16px; top: 11px; width: 18px; height: 18px; border-radius: 5px; background: var(--surface-2); color: var(--ink-2); font: 600 14px/18px var(--f-mono); text-align: center; }
.qa details[open] summary::before { content: "–"; background: var(--accent); color: var(--accent-ink); }
.qa .lvl { display: inline-block; font: 700 10px/1 var(--f-mono); color: var(--ink-3); border: 1px solid var(--rule); border-radius: 4px; padding: 3px 5px; margin-right: 8px; vertical-align: 2px; }
.qa .a { padding: 2px 18px 14px 44px; }
.qa .a > :last-child { margin-bottom: 0; }

/* references */
.refs ol { font-size: 15px; }
.refs li { margin: 6px 0; }

/* chapter footer nav */
.pager { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; margin-top: 56px; padding-top: 24px; border-top: 1px solid var(--rule); }
.pager a { display: block; padding: 14px 16px; border: 1px solid var(--rule); border-radius: 10px; text-decoration: none; background: var(--surface); }
.pager a:hover { border-color: var(--accent); }
.pager small { display: block; font: 500 11px var(--f-mono); color: var(--ink-3); text-transform: uppercase; letter-spacing: .08em; }
.pager span { font: 600 16px var(--f-display); color: var(--ink); }
.pager .next { text-align: right; grid-column: 2; }

/* ---------- home ---------- */
.home { max-width: 1100px; margin: 0 auto; }
.hero { display: grid; grid-template-columns: minmax(0, 1.25fr) minmax(0, 1fr); gap: 40px; align-items: center; padding: 20px 0 40px; border-bottom: 1px solid var(--rule); }
.hero h1 { font: 800 clamp(40px, 6.4vw, 72px)/0.98 var(--f-display); letter-spacing: -.035em; margin: 12px 0 18px; }
.hero h1 em { font-style: normal; color: var(--accent); }
.hero .lede { max-width: 54ch; }
.hero-eq { background: var(--surface); border: 1px solid var(--rule); border-radius: 14px; padding: 18px; box-shadow: var(--shadow); }
.hero-eq .eqline { font-size: clamp(14px, 1.5vw, 19px); display: flex; justify-content: safe center; padding: 10px 0 4px; overflow-x: auto; }
.hero-eq canvas { width: 100%; aspect-ratio: 16 / 10; display: block; border-radius: 8px; }
.hero-eq .cap { font: 12px/1.4 var(--f-mono); color: var(--ink-3); margin-top: 10px; }
.hero-cta { display: flex; flex-wrap: wrap; gap: 10px; margin-top: 8px; }
.btn { display: inline-flex; align-items: center; height: 42px; padding: 0 18px; border-radius: 10px; font: 600 15px var(--f-display); text-decoration: none; border: 1px solid var(--rule); color: var(--ink); background: var(--surface); }
.btn.primary { background: var(--accent); border-color: var(--accent); color: var(--accent-ink); }
.home h2 { font: 750 30px/1.15 var(--f-display); margin: 48px 0 6px; }
.home .sub { color: var(--ink-2); margin: 0 0 22px; max-width: 70ch; }
.paths { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 16px; }
.path { background: var(--surface); border: 1px solid var(--rule); border-radius: 14px; padding: 20px; display: flex; flex-direction: column; gap: 10px; }
.path h3 { margin: 0; font-size: 20px; }
.path p { margin: 0; font-size: 15px; color: var(--ink-2); }
.path ol { margin: 0; padding-left: 1.2em; font: 14px/1.6 var(--f-display); }
.path .weights { font: 12px var(--f-mono); color: var(--ink-3); }
.parts { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 16px; }
.part { background: var(--surface); border: 1px solid var(--rule); border-radius: 14px; padding: 18px 20px; }
.part h3 { margin: 0 0 10px; font-size: 13px; font-family: var(--f-mono); text-transform: uppercase; letter-spacing: .1em; color: var(--ink-3); }
.part a { display: grid; grid-template-columns: 32px minmax(0, 1fr) auto; gap: 8px; align-items: baseline; padding: 7px 0; border-top: 1px solid var(--rule); text-decoration: none; color: var(--ink); font-family: var(--f-display); }
.part a:first-of-type { border-top: 0; }
.part a .n { font: 500 12px var(--f-mono); color: var(--ink-3); }
.part a .t { font-weight: 600; font-size: 15.5px; }
.part a .d { grid-column: 2 / 4; font-size: 13px; color: var(--ink-2); font-weight: 400; }
.part a .rr { display: flex; gap: 4px; }
.part a:hover .t { color: var(--accent); }
.plan { overflow-x: auto; }
.plan table td:first-child { font: 600 13px var(--f-mono); white-space: nowrap; }
.progress-strip { display: flex; gap: 18px; flex-wrap: wrap; align-items: center; font: 13px var(--f-mono); color: var(--ink-2); margin-top: 18px; }
.bar { width: 200px; height: 8px; border-radius: 99px; background: var(--surface-2); overflow: hidden; }
.bar i { display: block; height: 100%; background: var(--key); width: 0; }
@media (max-width: 900px) { .hero { grid-template-columns: minmax(0, 1fr); } .paths, .parts { grid-template-columns: minmax(0, 1fr); } }

/* ---------- search ---------- */
.search-overlay { position: fixed; inset: 0; z-index: 60; background: color-mix(in srgb, var(--ink) 30%, transparent); display: flex; justify-content: center; align-items: flex-start; padding: 10vh 16px 16px; }
.search-box { width: min(680px, 100%); background: var(--surface); border: 1px solid var(--rule); border-radius: 14px; box-shadow: var(--shadow); overflow: hidden; }
.search-box input { width: 100%; border: 0; border-bottom: 1px solid var(--rule); padding: 16px 18px; font: 17px var(--f-display); background: transparent; color: var(--ink); outline: none; }
.search-results { max-height: 60vh; overflow-y: auto; }
.search-results a { display: block; padding: 10px 18px; text-decoration: none; color: var(--ink); border-bottom: 1px solid var(--rule); }
.search-results a:hover, .search-results a.sel { background: var(--accent-soft); }
.search-results small { display: block; font: 11px var(--f-mono); color: var(--ink-3); }
.search-results b { font: 600 15px var(--f-display); }
.search-results span { display: block; font-size: 13.5px; color: var(--ink-2); line-height: 1.4; }
.search-results mark { background: color-mix(in srgb, var(--accent) 25%, transparent); color: inherit; border-radius: 2px; }
.search-empty { padding: 18px; color: var(--ink-3); font: 14px var(--f-display); }

.loading { color: var(--ink-3); font: 14px var(--f-mono); padding: 40px 0; }

/* content-kind chips: theory, drills, coding */
.role.th { background: var(--accent-soft); color: var(--accent); }
.role.dr { background: var(--rs-soft); color: var(--rs); }
.role.cd { background: var(--key-soft); color: var(--key); }

/* drills: the question is always visible; the answer sits in a <details> */
.chapter > section { counter-reset: drill; }
.drill { counter-increment: drill; border: 1px solid var(--rule); border-radius: 12px; background: var(--surface); margin: 14px 0; padding: 14px 16px 6px; }
.drill > .dq { margin: 0 0 8px; font: 500 16px/1.5 var(--f-display); }
.drill > .dq::before { content: counter(drill) "."; font: 700 13px/1 var(--f-mono); color: var(--ink-3); margin-right: 8px; }
.drill .lvl { display: inline-block; font: 700 10px/1 var(--f-mono); text-transform: uppercase; letter-spacing: .04em; border-radius: 4px; padding: 3px 6px; margin-right: 8px; vertical-align: 2px; border: 1px solid var(--rule); color: var(--ink-3); }
.drill[data-kind="tricky"] .lvl { color: var(--trap, var(--rs)); border-color: currentColor; }
.drill[data-kind="output"] .lvl, .drill[data-kind="bug"] .lvl { color: var(--rs); border-color: currentColor; }
.drill[data-kind="code"] .lvl { color: var(--key); border-color: currentColor; }
.drill pre { margin: 10px 0; }
.drill details.q { border-top: 1px dashed var(--rule); margin: 10px -16px 0; }
.drill details.q > summary { cursor: pointer; list-style: none; padding: 10px 16px; font: 600 13px/1 var(--f-mono); color: var(--accent); }
.drill details.q > summary::-webkit-details-marker { display: none; }
.drill details.q > summary::before { content: "▸ "; }
.drill details.q[open] > summary::before { content: "▾ "; }
.drill details.q > .a { padding: 0 16px 12px; }
.drill details.q > .a > :last-child { margin-bottom: 0; }
pre.out { background: var(--surface-2); white-space: pre; padding: 0 16px 12px; font: 13px/1.55 var(--f-mono); }
pre.out::before { content: "output"; display: block; margin: 0 -16px; padding: 8px 16px 6px; font: 600 10px/1 var(--f-mono); text-transform: uppercase; letter-spacing: .06em; color: var(--ink-3); }
p.rating { font: 500 13px/1.5 var(--f-mono); color: var(--ink-2); background: var(--key-soft); border-radius: 8px; padding: 6px 10px; }
.reveal-all { font: 600 12px/1 var(--f-mono); border: 1px solid var(--rule); background: var(--surface-2); color: var(--ink-2); border-radius: 6px; padding: 6px 10px; cursor: pointer; margin: 4px 0 8px; }
:not(pre) > code { overflow-wrap: anywhere; }
.chapter h2, .chapter h3, .chapter h4 { overflow-wrap: anywhere; }

/* ---------- standalone: CSS-only routing ---------- */
.chwrap { display: none; }
.chwrap:target, .chwrap:has(:target) { display: grid; }
.rail a.cur { background: var(--accent-soft); color: var(--ink); font-weight: 600; }
.kind, #menu-toggle { position: absolute; opacity: 0; pointer-events: none; }
.roles label { display: inline-flex; align-items: center; color: var(--ink-2); font: 600 12px/1 var(--f-display); padding: 0 10px; height: 32px; cursor: pointer; letter-spacing: .02em; }
.roles label + label { border-left: 1px solid var(--rule); }
body:has(#k-all:checked) .roles label[for="k-all"], body:has(#k-th:checked) .roles label[for="k-th"],
body:has(#k-dr:checked) .roles label[for="k-dr"], body:has(#k-cd:checked) .roles label[for="k-cd"] { background: var(--accent); color: var(--accent-ink); }
body:has(#k-th:checked) .chapter > section:not([data-roles~="th"]),
body:has(#k-dr:checked) .chapter > section:not([data-roles~="dr"]),
body:has(#k-cd:checked) .chapter > section:not([data-roles~="cd"]) { display: none; }
@media (max-width: 900px) { body:has(#menu-toggle:checked) .rail { transform: none; } }
p.formula { text-align: center; }
.no-js-hide { display: none; }
body.js .no-js-hide { display: inline-flex; }