/* ==========================================================================
   Tech Interview Handbook — shared stylesheet
   ========================================================================== */

:root {
  --bg: #fbfbfd;
  --bg-soft: #f3f4f8;
  --surface: #ffffff;
  --border: #e6e8ef;
  --border-strong: #d4d8e3;
  --text: #1c2030;
  --text-dim: #525b73;
  --text-mute: #8a91a6;
  --accent: #4f46e5;
  --accent-soft: #eef0ff;
  --accent-text: #3f37c9;
  --green: #0f9f6e;
  --green-soft: #e8f7f1;
  --amber: #b7791f;
  --amber-soft: #fdf6e7;
  --red: #d64545;
  --red-soft: #fdeeee;
  --violet: #7c3aed;
  --violet-soft: #f4efff;
  --code-bg: #f5f6fa;
  --code-text: #2a2f45;
  --diagram-bg: #0f1422;
  --diagram-text: #d9e1ff;
  --shadow: 0 1px 2px rgba(20, 24, 40, .04), 0 4px 16px rgba(20, 24, 40, .05);
  --radius: 12px;
  --radius-sm: 8px;
  --topbar-h: 58px;
  --sidebar-w: 272px;
  --toc-w: 232px;
  --content-w: 800px;
  --font: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, "Noto Sans", sans-serif;
  --mono: ui-monospace, "Cascadia Code", "SF Mono", Menlo, Consolas, "Liberation Mono", monospace;
}

html[data-theme="dark"] {
  --bg: #0e1016;
  --bg-soft: #141720;
  --surface: #161a24;
  --border: #242a38;
  --border-strong: #323a4d;
  --text: #e6e9f2;
  --text-dim: #a7afc4;
  --text-mute: #717a92;
  --accent: #8b93ff;
  --accent-soft: #1f2340;
  --accent-text: #aab0ff;
  --green: #34d399;
  --green-soft: #12291f;
  --amber: #fbbf24;
  --amber-soft: #2a2312;
  --red: #f87171;
  --red-soft: #2c1616;
  --violet: #b794ff;
  --violet-soft: #221a36;
  --code-bg: #1b2030;
  --code-text: #dbe2f7;
  --diagram-bg: #0a0d16;
  --shadow: 0 1px 2px rgba(0, 0, 0, .3), 0 4px 16px rgba(0, 0, 0, .25);
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; scroll-padding-top: calc(var(--topbar-h) + 16px); -webkit-text-size-adjust: 100%; }
body {
  margin: 0;
  font-family: var(--font);
  font-size: 16px;
  line-height: 1.7;
  color: var(--text);
  background: var(--bg);
  -webkit-font-smoothing: antialiased;
}
a { color: var(--accent-text); text-decoration: none; }
a:hover { text-decoration: underline; }
img, svg { max-width: 100%; }
hr { border: 0; border-top: 1px solid var(--border); margin: 32px 0; }
::selection { background: var(--accent-soft); }

/* ---------- Top bar ---------- */
.topbar {
  position: sticky; top: 0; z-index: 50;
  height: var(--topbar-h);
  display: flex; align-items: center; gap: 12px;
  padding: 0 20px;
  background: color-mix(in srgb, var(--bg) 88%, transparent);
  backdrop-filter: saturate(160%) blur(12px);
  -webkit-backdrop-filter: saturate(160%) blur(12px);
  border-bottom: 1px solid var(--border);
}
.brand { display: flex; align-items: center; gap: 10px; font-weight: 700; color: var(--text); font-size: 15px; white-space: nowrap; }
.brand:hover { text-decoration: none; }
.brand-mark {
  width: 30px; height: 30px; border-radius: 9px;
  display: grid; place-items: center;
  background: linear-gradient(135deg, #4f46e5, #7c3aed 60%, #db2777);
  color: #fff; font-size: 13px; font-weight: 800; letter-spacing: -.5px;
}
.topbar-spacer { flex: 1; }
.topnav { display: flex; gap: 2px; }
.topnav a { color: var(--text-dim); font-size: 14px; padding: 6px 10px; border-radius: 8px; }
.topnav a:hover, .topnav a.active { background: var(--bg-soft); color: var(--text); text-decoration: none; }
.search-trigger {
  display: flex; align-items: center; gap: 8px;
  min-width: 220px; padding: 7px 10px 7px 12px;
  font: inherit; font-size: 14px; color: var(--text-mute);
  background: var(--bg-soft); border: 1px solid var(--border); border-radius: 9px; cursor: pointer;
}
.search-trigger:hover { border-color: var(--border-strong); }
.search-trigger kbd, .kbd {
  margin-left: auto; font-family: var(--mono); font-size: 11px;
  padding: 1px 6px; border: 1px solid var(--border-strong); border-radius: 5px; color: var(--text-mute); background: var(--surface);
}
.icon-btn {
  width: 36px; height: 36px; display: grid; place-items: center;
  background: transparent; border: 1px solid transparent; border-radius: 9px; color: var(--text-dim); cursor: pointer;
}
.icon-btn:hover { background: var(--bg-soft); border-color: var(--border); color: var(--text); }
.icon-btn svg { width: 18px; height: 18px; }
.menu-btn { display: none; }

/* ---------- Layout ---------- */
.layout { display: flex; align-items: flex-start; }
.sidebar {
  position: sticky; top: var(--topbar-h);
  width: var(--sidebar-w); flex-shrink: 0;
  height: calc(100vh - var(--topbar-h));
  overflow-y: auto;
  padding: 20px 14px 40px 18px;
  border-right: 1px solid var(--border);
  background: var(--bg);
}
.sidebar-group { margin-bottom: 18px; }
.sidebar-title {
  display: flex; align-items: center; gap: 8px;
  font-size: 12px; font-weight: 700; text-transform: uppercase; letter-spacing: .06em;
  color: var(--text-mute); padding: 4px 10px; margin-bottom: 2px;
}
.sidebar a {
  display: block; padding: 5px 10px; margin: 1px 0; border-radius: 7px;
  color: var(--text-dim); font-size: 14px; line-height: 1.45;
}
.sidebar a:hover { background: var(--bg-soft); color: var(--text); text-decoration: none; }
.sidebar a.active { background: var(--accent-soft); color: var(--accent-text); font-weight: 600; }
.dot { width: 8px; height: 8px; border-radius: 50%; flex-shrink: 0; }
.track-group { margin-bottom: 4px; }
.track-title {
  width: 100%; display: flex; align-items: center; gap: 9px;
  padding: 8px 10px; border: 0; border-radius: 8px; cursor: pointer;
  background: transparent; color: var(--text); font: 650 14px var(--font); text-align: left;
}
.track-title:hover { background: var(--bg-soft); }
.track-title .dot { width: 10px; height: 10px; }
.track-name { flex: 1; }
.track-count { font-size: 11px; font-weight: 600; color: var(--text-mute); background: var(--bg-soft); border: 1px solid var(--border); border-radius: 999px; padding: 0 7px; }
.chev { width: 7px; height: 7px; border-right: 2px solid var(--text-mute); border-bottom: 2px solid var(--text-mute); transform: rotate(-45deg); transition: transform .15s; margin-right: 3px; }
.track-group.open .chev { transform: rotate(45deg); }
.track-body { display: none; padding: 2px 0 10px 12px; margin-left: 14px; border-left: 1px solid var(--border); }
.track-group.open .track-body { display: block; }
.sidebar-section { font-size: 11px; font-weight: 700; text-transform: uppercase; letter-spacing: .06em; color: var(--text-mute); padding: 10px 10px 3px; }
.sidebar-section:first-child { padding-top: 4px; }

.main { flex: 1; min-width: 0; display: flex; justify-content: center; gap: 40px; padding: 36px 32px 80px; }
.doc { width: 100%; max-width: var(--content-w); min-width: 0; }
.main.wide .doc { max-width: 1080px; }

.toc {
  position: sticky; top: calc(var(--topbar-h) + 36px);
  width: var(--toc-w); flex-shrink: 0;
  max-height: calc(100vh - var(--topbar-h) - 60px); overflow-y: auto;
  font-size: 13px;
}
.toc-title { font-size: 12px; font-weight: 700; text-transform: uppercase; letter-spacing: .06em; color: var(--text-mute); margin-bottom: 8px; }
.toc a { display: block; padding: 4px 0 4px 12px; color: var(--text-mute); border-left: 2px solid var(--border); line-height: 1.4; }
.toc a:hover { color: var(--text); text-decoration: none; }
.toc a.active { color: var(--accent-text); border-left-color: var(--accent); font-weight: 600; }

/* ---------- Typography in docs ---------- */
.doc h1 { font-size: clamp(30px, 4vw, 40px); line-height: 1.15; letter-spacing: -.02em; margin: 6px 0 12px; font-weight: 800; }
.doc h2 {
  font-size: 26px; line-height: 1.25; letter-spacing: -.01em; font-weight: 750;
  margin: 56px 0 14px; padding-top: 8px;
}
.doc section:first-of-type h2 { margin-top: 24px; }
.doc h3 { font-size: 19px; line-height: 1.35; margin: 32px 0 10px; font-weight: 700; }
.doc h4 { font-size: 16px; margin: 20px 0 6px; font-weight: 700; }
.doc p { margin: 0 0 14px; }
.doc ul, .doc ol { padding-left: 22px; margin: 0 0 16px; }
.doc li { margin: 4px 0; }
.doc li > ul, .doc li > ol { margin: 4px 0; }
.doc strong, .doc b { font-weight: 650; }
.heading-anchor { opacity: 0; margin-left: 8px; color: var(--text-mute); font-weight: 400; }
h2:hover .heading-anchor, h3:hover .heading-anchor { opacity: 1; }

.crumb { font-size: 13px; font-weight: 600; color: var(--accent-text); text-transform: uppercase; letter-spacing: .06em; }
.lede { font-size: 18px; color: var(--text-dim); margin: 0 0 18px; }
.meta { display: flex; flex-wrap: wrap; gap: 8px; margin: 0 0 8px; }
.chip {
  display: inline-flex; align-items: center; gap: 6px;
  font-size: 13px; color: var(--text-dim);
  padding: 3px 10px; border: 1px solid var(--border); border-radius: 999px; background: var(--surface);
}
.doc-hero { padding-bottom: 20px; border-bottom: 1px solid var(--border); margin-bottom: 8px; }
.crumb a { color: inherit; }
.crumb-sep { margin: 0 8px; color: var(--text-mute); }
.chip.level { font-weight: 650; border-color: transparent; }
.chip.lvl-beginner { color: var(--green); background: var(--green-soft); }
.chip.lvl-intermediate { color: var(--accent-text); background: var(--accent-soft); }
.chip.lvl-advanced { color: var(--violet); background: var(--violet-soft); }
.chip.lvl-all-levels { color: var(--amber); background: var(--amber-soft); }
.prereq { font-size: 14px; color: var(--text-dim); margin: 6px 0 0 !important; }

/* ---------- Code ---------- */
code {
  font-family: var(--mono); font-size: .86em;
  background: var(--code-bg); color: var(--code-text);
  padding: 2px 6px; border-radius: 5px; border: 1px solid var(--border);
  word-break: break-word;
}
pre {
  position: relative;
  font-family: var(--mono); font-size: 13px; line-height: 1.6;
  background: var(--code-bg); color: var(--code-text);
  border: 1px solid var(--border); border-radius: var(--radius-sm);
  padding: 14px 16px; margin: 0 0 18px; overflow-x: auto;
}
pre code { background: none; border: 0; padding: 0; font-size: inherit; color: inherit; word-break: normal; }
pre.diagram {
  background: var(--diagram-bg); color: var(--diagram-text); border-color: transparent;
  font-size: 12.5px; line-height: 1.5; white-space: pre;
}
.copy-btn {
  position: absolute; top: 8px; right: 8px;
  font: 600 11px var(--font); padding: 3px 8px; border-radius: 6px; cursor: pointer;
  background: var(--surface); color: var(--text-dim); border: 1px solid var(--border);
  opacity: 0; transition: opacity .15s;
}
pre:hover .copy-btn { opacity: 1; }
pre.diagram .copy-btn { background: #1d2437; color: #aab4d6; border-color: #2b3450; }

/* ---------- Tables ---------- */
.table-wrap { overflow-x: auto; margin: 0 0 18px; border: 1px solid var(--border); border-radius: var(--radius-sm); }
.doc table { width: 100%; border-collapse: collapse; font-size: 14px; line-height: 1.55; }
.doc th, .doc td { padding: 9px 12px; text-align: left; vertical-align: top; border-bottom: 1px solid var(--border); }
.doc th { background: var(--bg-soft); font-weight: 650; font-size: 13px; color: var(--text); white-space: nowrap; }
.doc tr:last-child td { border-bottom: 0; }
.doc td + td, .doc th + th { border-left: 1px solid var(--border); }

/* ---------- Content components ---------- */
.analogy {
  position: relative;
  margin: 18px 0 20px; padding: 16px 18px 14px 56px;
  background: var(--amber-soft); border: 1px solid color-mix(in srgb, var(--amber) 28%, transparent);
  border-radius: var(--radius);
}
.analogy::before {
  content: ""; position: absolute; left: 18px; top: 17px; width: 24px; height: 24px;
  background: var(--amber);
  -webkit-mask: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='black' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpath d='M9 18h6M10 22h4M12 2a7 7 0 0 0-4 12.7c.6.5 1 1.3 1 2.1V17h6v-.2c0-.8.4-1.6 1-2.1A7 7 0 0 0 12 2z'/%3E%3C/svg%3E") center / contain no-repeat;
          mask: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='black' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpath d='M9 18h6M10 22h4M12 2a7 7 0 0 0-4 12.7c.6.5 1 1.3 1 2.1V17h6v-.2c0-.8.4-1.6 1-2.1A7 7 0 0 0 12 2z'/%3E%3C/svg%3E") center / contain no-repeat;
}
.analogy-title { font-weight: 700; color: var(--amber); font-size: 13px; text-transform: uppercase; letter-spacing: .05em; margin-bottom: 4px; }
.analogy p:last-child, .callout p:last-child { margin-bottom: 0; }

.callout {
  margin: 16px 0 20px; padding: 13px 16px;
  border-radius: var(--radius-sm); border: 1px solid var(--border); border-left: 4px solid var(--accent);
  background: var(--accent-soft);
}
.callout > strong:first-child { display: block; margin-bottom: 2px; }
.callout.tip { border-left-color: var(--green); background: var(--green-soft); }
.callout.warn { border-left-color: var(--red); background: var(--red-soft); }
.callout.interview { border-left-color: var(--violet); background: var(--violet-soft); }
.callout ul { margin-bottom: 0; }

.tldr {
  margin: 20px 0 8px; padding: 18px 20px;
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius); box-shadow: var(--shadow);
}
.tldr-title { font-size: 12px; font-weight: 700; text-transform: uppercase; letter-spacing: .06em; color: var(--accent-text); margin-bottom: 6px; }
.tldr ul { margin: 0; }

.cards { display: grid; grid-template-columns: repeat(auto-fill, minmax(230px, 1fr)); gap: 14px; margin: 0 0 20px; }
.card {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 16px 18px; box-shadow: var(--shadow);
}
a.card { color: var(--text); transition: border-color .15s, transform .15s; }
a.card:hover { border-color: var(--accent); text-decoration: none; transform: translateY(-2px); }
.card h4 { margin: 0 0 6px; font-size: 15.5px; }
.card p, .card ul { font-size: 14.5px; color: var(--text-dim); margin-bottom: 0; }
.card p + p { margin-top: 8px; }

ol.steps { list-style: none; counter-reset: step; padding-left: 0; margin: 0 0 20px; }
ol.steps > li {
  counter-increment: step; position: relative;
  padding: 2px 0 14px 46px; margin: 0;
  border-left: 2px solid var(--border); margin-left: 15px; padding-left: 30px;
}
ol.steps > li:last-child { border-left-color: transparent; padding-bottom: 0; }
ol.steps > li::before {
  content: counter(step);
  position: absolute; left: -16px; top: 0;
  width: 30px; height: 30px; border-radius: 50%;
  display: grid; place-items: center;
  font-size: 13px; font-weight: 700;
  background: var(--surface); color: var(--accent-text); border: 2px solid var(--accent);
}
ol.steps > li > b:first-child, ol.steps > li > strong:first-child { display: block; }

.compare { display: grid; grid-template-columns: 1fr 1fr; gap: 14px; margin: 0 0 20px; }
.compare > div { border: 1px solid var(--border); border-radius: var(--radius); padding: 14px 16px; background: var(--surface); }
.compare h4 { margin-top: 0; }

.formula {
  margin: 14px 0 18px; padding: 14px 18px;
  font-family: "Cambria Math", "Times New Roman", Georgia, serif; font-size: 18px; line-height: 1.8;
  text-align: center; overflow-x: auto;
  background: var(--bg-soft); border: 1px solid var(--border); border-radius: var(--radius-sm);
}
.formula .where { display: block; margin-top: 6px; font-family: var(--font); font-size: 14px; color: var(--text-dim); text-align: left; }

.tag {
  display: inline-block; font-size: 11px; font-weight: 700; letter-spacing: .03em;
  padding: 1px 8px; border-radius: 999px; vertical-align: middle;
  background: var(--bg-soft); color: var(--text-dim); border: 1px solid var(--border);
}

dl.glossary { display: grid; grid-template-columns: minmax(120px, 200px) 1fr; gap: 0; margin: 0 0 20px; border: 1px solid var(--border); border-radius: var(--radius-sm); overflow: hidden; }
dl.glossary dt, dl.glossary dd { margin: 0; padding: 9px 12px; border-bottom: 1px solid var(--border); font-size: 14.5px; }
dl.glossary dt { font-weight: 650; background: var(--bg-soft); font-family: var(--mono); font-size: 13.5px; }
dl.glossary dt:nth-last-of-type(1), dl.glossary dd:last-of-type { border-bottom: 0; }

ul.keypoints { list-style: none; padding: 0; margin: 0 0 20px; display: grid; gap: 8px; }
ul.keypoints li {
  position: relative; margin: 0; padding: 10px 14px 10px 38px;
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius-sm); font-size: 15px;
}
ul.keypoints li::before {
  content: ""; position: absolute; left: 14px; top: 17px; width: 10px; height: 10px; border-radius: 3px;
  background: var(--accent); transform: rotate(45deg);
}

/* ---------- Q&A ---------- */
.qa-toolbar {
  position: sticky; top: var(--topbar-h); z-index: 5;
  display: flex; flex-wrap: wrap; align-items: center; gap: 8px;
  margin: 0 0 16px; padding: 10px 0;
  background: var(--bg);
}
.qa-search {
  flex: 1; min-width: 180px;
  font: inherit; font-size: 14px; color: var(--text);
  padding: 8px 12px; border: 1px solid var(--border); border-radius: 9px; background: var(--surface);
}
.qa-search:focus, .search-input:focus { outline: 2px solid var(--accent); outline-offset: -1px; border-color: transparent; }
.btn {
  font: inherit; font-size: 13px; font-weight: 600; cursor: pointer;
  padding: 7px 12px; border-radius: 9px; border: 1px solid var(--border); background: var(--surface); color: var(--text-dim);
}
.btn:hover { border-color: var(--border-strong); color: var(--text); }
.btn.on { background: var(--accent); color: #fff; border-color: var(--accent); }
.btn.primary { background: var(--accent); color: #fff; border-color: var(--accent); }
.qa-count { font-size: 13px; color: var(--text-mute); }

.qa-group { margin: 0 0 26px; }
.qa-group > h3 { margin-top: 20px; }
details.qa {
  border: 1px solid var(--border); border-radius: var(--radius-sm);
  background: var(--surface); margin: 0 0 8px;
  transition: border-color .15s, box-shadow .15s;
}
details.qa:hover { border-color: var(--border-strong); }
details.qa[open] { box-shadow: var(--shadow); border-color: var(--border-strong); }
details.qa > summary {
  list-style: none; cursor: pointer;
  display: flex; gap: 12px; align-items: flex-start;
  padding: 12px 16px; font-weight: 600; font-size: 15.5px; line-height: 1.5;
}
details.qa > summary::-webkit-details-marker { display: none; }
details.qa > summary::before {
  content: ""; flex-shrink: 0; margin-top: 7px;
  width: 8px; height: 8px; border-right: 2px solid var(--text-mute); border-bottom: 2px solid var(--text-mute);
  transform: rotate(-45deg); transition: transform .15s;
}
details.qa[open] > summary::before { transform: rotate(45deg); margin-top: 5px; }
.qa-num { color: var(--text-mute); font-weight: 600; font-variant-numeric: tabular-nums; min-width: 26px; }
.qa-level { margin-left: auto; flex-shrink: 0; }
.qa-level.basic { color: var(--green); background: var(--green-soft); border-color: transparent; }
.qa-level.intermediate { color: var(--accent-text); background: var(--accent-soft); border-color: transparent; }
.qa-level.advanced { color: var(--violet); background: var(--violet-soft); border-color: transparent; }
.qa-level.scenario { color: var(--amber); background: var(--amber-soft); border-color: transparent; }
details.qa > .answer { padding: 2px 18px 14px 44px; font-size: 15px; color: var(--text); border-top: 1px dashed var(--border); padding-top: 12px; }
details.qa > .answer > :last-child { margin-bottom: 0; }
details.qa.hidden, .qa-group.hidden { display: none; }
.qa-source { font-size: 13px; margin-top: 8px; }
mark { background: color-mix(in srgb, var(--amber) 35%, transparent); color: inherit; border-radius: 3px; padding: 0 1px; }

/* ---------- Prev / next ---------- */
.pager { display: grid; grid-template-columns: 1fr 1fr; gap: 14px; margin-top: 56px; }
.pager a {
  display: block; padding: 14px 18px; border: 1px solid var(--border); border-radius: var(--radius);
  background: var(--surface); color: var(--text);
}
.pager a:hover { border-color: var(--accent); text-decoration: none; }
.pager small { display: block; color: var(--text-mute); font-size: 12px; text-transform: uppercase; letter-spacing: .06em; }
.pager .next { text-align: right; grid-column: 2; }
.site-footer { text-align: center; color: var(--text-mute); font-size: 13px; padding: 30px 0 10px; border-top: 1px solid var(--border); margin-top: 48px; }

/* ---------- Search overlay ---------- */
.search-overlay {
  position: fixed; inset: 0; z-index: 100;
  display: none; align-items: flex-start; justify-content: center;
  padding: 10vh 16px 16px;
  background: rgba(10, 12, 20, .45); backdrop-filter: blur(3px);
}
.search-overlay.open { display: flex; }
.search-box {
  width: 100%; max-width: 680px; max-height: 76vh;
  display: flex; flex-direction: column;
  background: var(--surface); border: 1px solid var(--border); border-radius: 14px;
  box-shadow: 0 24px 60px rgba(0, 0, 0, .3); overflow: hidden;
}
.search-head { display: flex; align-items: center; gap: 10px; padding: 12px 16px; border-bottom: 1px solid var(--border); }
.search-head svg { width: 18px; height: 18px; color: var(--text-mute); flex-shrink: 0; }
.search-input { flex: 1; font: inherit; font-size: 17px; border: 0; background: transparent; color: var(--text); padding: 4px 2px; }
.search-results { overflow-y: auto; padding: 6px; }
.search-results a {
  display: block; padding: 10px 12px; border-radius: 9px; color: var(--text);
}
.search-results a:hover, .search-results a.sel { background: var(--accent-soft); text-decoration: none; }
.sr-title { font-weight: 600; font-size: 14.5px; line-height: 1.4; }
.sr-meta { display: flex; gap: 8px; align-items: center; font-size: 12px; color: var(--text-mute); margin-top: 2px; }
.sr-snip { font-size: 13px; color: var(--text-dim); margin-top: 3px; display: -webkit-box; -webkit-line-clamp: 2; -webkit-box-orient: vertical; overflow: hidden; }
.search-empty { padding: 28px 16px; text-align: center; color: var(--text-mute); font-size: 14px; }
.search-foot { display: flex; gap: 16px; padding: 8px 16px; border-top: 1px solid var(--border); font-size: 12px; color: var(--text-mute); }

/* ---------- Home ---------- */
.home-hero { text-align: center; padding: 40px 0 28px; }
.home-hero h1 { font-size: clamp(34px, 5vw, 52px); margin: 10px 0 14px; }
.grad-text { background: linear-gradient(135deg, #4f46e5, #7c3aed 55%, #db2777); -webkit-background-clip: text; background-clip: text; color: transparent; }
.home-hero .lede { max-width: 660px; margin: 0 auto 24px; }
.hero-search {
  display: flex; align-items: center; gap: 10px; width: 100%; max-width: 560px; margin: 0 auto;
  padding: 13px 16px; font: inherit; font-size: 16px; color: var(--text-mute); cursor: pointer;
  background: var(--surface); border: 1px solid var(--border-strong); border-radius: 12px; box-shadow: var(--shadow);
}
.hero-search svg { width: 18px; height: 18px; }
.stats { display: flex; justify-content: center; flex-wrap: wrap; gap: 28px; margin: 28px 0 8px; }
.stat b { display: block; font-size: 26px; font-weight: 800; letter-spacing: -.02em; }
.stat span { font-size: 13px; color: var(--text-mute); }
.home-section { margin: 44px 0 0; }
.home-section-head { display: flex; align-items: center; gap: 10px; margin-bottom: 4px; }
.home-section-head h2 { margin: 0 !important; padding: 0; font-size: 22px; }
.home-section > p { color: var(--text-dim); margin: 0 0 14px; }
.topic-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(280px, 1fr)); gap: 14px; }
.topic-card {
  display: flex; flex-direction: column;
  padding: 18px; border: 1px solid var(--border); border-radius: var(--radius);
  background: var(--surface); color: var(--text); box-shadow: var(--shadow);
  transition: transform .15s, border-color .15s;
}
.topic-card:hover { transform: translateY(-2px); border-color: var(--accent); text-decoration: none; }
.topic-card h3 { margin: 0 0 6px !important; font-size: 16.5px; }
.topic-card p { margin: 0 0 12px; font-size: 14px; color: var(--text-dim); flex: 1; }
.topic-card .meta { margin: 0; }
.topic-card .chip { font-size: 12px; }
.track-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(230px, 1fr)); gap: 14px; margin: 8px 0 0; }
.track-card, .topic-card { position: relative; overflow: hidden; }
.track-card {
  display: flex; flex-direction: column; padding: 20px 18px 16px;
  border: 1px solid var(--border); border-radius: var(--radius); background: var(--surface); color: var(--text); box-shadow: var(--shadow);
  transition: transform .15s, border-color .15s;
}
.track-card:hover { transform: translateY(-2px); border-color: var(--track); text-decoration: none; }
.track-card .track-bar, .home-track-head .track-bar { display: block; background: var(--track); border-radius: 4px; }
.track-card .track-bar { position: absolute; left: 0; top: 0; right: 0; height: 4px; border-radius: 0; }
.track-card h3 { margin: 0 0 6px !important; font-size: 17px; }
.track-card p { font-size: 14px; color: var(--text-dim); margin: 0 0 12px; flex: 1; }
.home-track { padding-top: 12px; }
.home-track-head { display: flex; gap: 14px; align-items: stretch; margin-bottom: 6px; }
.home-track-head .track-bar { width: 5px; flex-shrink: 0; }
.home-track-head h2 { margin: 0 0 2px !important; padding: 0; font-size: 26px; }
.home-track-head p { margin: 0; color: var(--text-dim); }
.home-sub { margin: 22px 0 0; }
.home-sub-title { font-size: 13px !important; text-transform: uppercase; letter-spacing: .06em; color: var(--text-mute); margin: 0 0 2px !important; }
.home-sub-blurb { margin: 0 0 12px; font-size: 14.5px; color: var(--text-dim); }
.topic-card { border-top: 3px solid var(--track, var(--border)); }
.topic-card:hover { border-color: var(--track, var(--accent)); }
.topic-num {
  position: absolute; top: 14px; right: 14px; width: 24px; height: 24px; border-radius: 50%;
  display: grid; place-items: center; font-size: 12px; font-weight: 700;
  color: var(--text-mute); background: var(--bg-soft); border: 1px solid var(--border);
}
.topic-card h3 { padding-right: 30px; }
.start-here { display: grid; grid-template-columns: repeat(auto-fill, minmax(220px, 1fr)); gap: 12px; margin: 10px 0 0; counter-reset: sh; }
.start-here div { padding: 14px 16px; border-radius: var(--radius); background: var(--bg-soft); border: 1px solid var(--border); font-size: 14.5px; color: var(--text-dim); }
.start-here b { display: block; color: var(--text); margin-bottom: 2px; }
.paths { display: grid; grid-template-columns: repeat(auto-fill, minmax(300px, 1fr)); gap: 14px; }
.path { padding: 16px 18px; border: 1px dashed var(--border-strong); border-radius: var(--radius); }
.path h4 { margin: 0 0 8px; }
.path ol { margin: 0; padding-left: 20px; font-size: 14.5px; }

/* ---------- Revision / glossary pages ---------- */
.rev-topic { margin: 0 0 30px; }
.filter-bar { display: flex; flex-wrap: wrap; gap: 8px; margin: 0 0 20px; }

/* ---------- Responsive ---------- */
@media (max-width: 1240px) { .toc { display: none; } }
@media (max-width: 920px) {
  .menu-btn { display: grid; }
  .topnav { display: none; }
  .search-trigger { min-width: 0; }
  .search-trigger span, .search-trigger kbd { display: none; }
  .sidebar {
    position: fixed; left: 0; top: var(--topbar-h); z-index: 40;
    transform: translateX(-100%); transition: transform .2s;
    box-shadow: var(--shadow); background: var(--bg);
  }
  body.nav-open .sidebar { transform: none; }
  body.nav-open::after { content: ""; position: fixed; inset: var(--topbar-h) 0 0 0; background: rgba(0,0,0,.3); z-index: 30; }
  .main { padding: 24px 18px 60px; }
}
@media (max-width: 640px) {
  body { font-size: 15.5px; }
  .compare { grid-template-columns: 1fr; }
  dl.glossary { grid-template-columns: 1fr; }
  dl.glossary dt { border-bottom: 0; }
  details.qa > .answer { padding-left: 18px; }
  .qa-level { display: none; }
  .pager { grid-template-columns: 1fr; }
  .pager .next { grid-column: 1; }
  .brand-name { display: none; }
}

@media print {
  .topbar, .sidebar, .toc, .qa-toolbar, .pager, .copy-btn { display: none !important; }
  .main { padding: 0; }
  details.qa > .answer { display: block !important; }
  pre.diagram { background: #fff; color: #000; border: 1px solid #ccc; }
}