/* =========================================================================
   Quant Finance Interview Bank — lockin interview mode, "Claude" style.
   Restyle = swap the token block below; every component reads only tokens.
   ========================================================================= */

:root {
  --bg: #f0eee6;        --surface: #faf9f5;   --surface-2: #e8e6dc;
  --ink: #141413;       --muted: #6e6d66;
  --accent: #d97757;    --on-accent: #ffffff;
  --accent-soft: rgba(217, 119, 87, 0.12);
  --border: rgba(20, 20, 19, 0.10);
  --border-strong: rgba(20, 20, 19, 0.18);
  --radius: 12px;       --radius-lg: 18px;     --radius-sm: 8px;
  --shadow: 0 1px 3px rgba(20, 20, 19, 0.07);
  --shadow-lg: 0 8px 30px rgba(20, 20, 19, 0.12);
  --font-display: ui-serif, Georgia, 'Times New Roman', serif;
  --font-body: system-ui, -apple-system, 'Segoe UI', sans-serif;
  --font-mono: ui-monospace, 'SF Mono', Menlo, monospace;
  --ok: #7d9a6f;   --warn: #c58c33;   --err: #b0552f;
  --sidebar-w: 320px;
  --reader-max: 820px;
}

:root[data-theme="dark"],
html[data-theme="dark"] {
  --bg: #1f1e1b;        --surface: #262521;   --surface-2: #302e29;
  --ink: #f0eee6;       --muted: #a3a094;
  --accent: #e08a6d;    --on-accent: #1f1e1b;
  --accent-soft: rgba(224, 138, 109, 0.16);
  --border: rgba(240, 238, 230, 0.12);
  --border-strong: rgba(240, 238, 230, 0.22);
  --shadow: 0 1px 3px rgba(0, 0, 0, 0.4);
  --shadow-lg: 0 8px 30px rgba(0, 0, 0, 0.5);
  --ok: #8fae80;   --warn: #d6a44e;   --err: #d47a55;
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #1f1e1b;        --surface: #262521;   --surface-2: #302e29;
    --ink: #f0eee6;       --muted: #a3a094;
    --accent: #e08a6d;    --on-accent: #1f1e1b;
    --accent-soft: rgba(224, 138, 109, 0.16);
    --border: rgba(240, 238, 230, 0.12);
    --border-strong: rgba(240, 238, 230, 0.22);
    --shadow: 0 1px 3px rgba(0, 0, 0, 0.4);
    --shadow-lg: 0 8px 30px rgba(0, 0, 0, 0.5);
    --ok: #8fae80;   --warn: #d6a44e;   --err: #d47a55;
  }
}

/* ---------- reset / base ---------- */
* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; }
body {
  background: var(--bg);
  color: var(--ink);
  font-family: var(--font-body);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}
h1, h2, h3, h4 { font-family: var(--font-display); font-weight: 600; line-height: 1.25; }
a { color: var(--accent); text-underline-offset: 2px; }
a:hover { text-decoration: underline; }
button { font-family: inherit; cursor: pointer; }
code, pre, kbd { font-family: var(--font-mono); }
:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; border-radius: 4px; }

.skip-link {
  position: absolute; left: -999px; top: 0; z-index: 100;
  background: var(--accent); color: var(--on-accent);
  padding: 8px 14px; border-radius: 0 0 var(--radius-sm) 0;
}
.skip-link:focus { left: 0; }

/* ---------- layout ---------- */
.layout { display: grid; grid-template-columns: var(--sidebar-w) minmax(0, 1fr); min-height: 100vh; }

/* ---------- sidebar ---------- */
.sidebar {
  position: sticky; top: 0; align-self: start;
  height: 100vh; overflow-y: auto;
  background: var(--surface);
  border-right: 1px solid var(--border);
  padding: 20px 14px 40px;
  display: flex; flex-direction: column; gap: 14px;
}
.side-head { padding: 4px 8px; }
.side-brand {
  font-family: var(--font-display); font-size: 1.16rem; font-weight: 700;
  color: var(--ink); text-decoration: none; display: block; line-height: 1.2;
}
.side-brand:hover { text-decoration: none; color: var(--accent); }
.side-sub { color: var(--muted); font-size: 0.8rem; margin-top: 3px; }

.side-progress {
  display: flex; gap: 8px; padding: 4px 8px; flex-wrap: wrap;
}
.side-progress .pill {
  font-size: 0.72rem; color: var(--muted);
  background: var(--surface-2); border: 1px solid var(--border);
  border-radius: 999px; padding: 3px 9px; white-space: nowrap;
}
.side-progress .pill b { color: var(--ink); font-weight: 600; }

.side-nav { display: flex; flex-direction: column; gap: 2px; }
.cat-group { border-radius: var(--radius-sm); }
.cat-toggle {
  width: 100%; display: flex; align-items: center; gap: 8px;
  background: none; border: none; color: var(--ink);
  padding: 8px 8px; border-radius: var(--radius-sm);
  font-size: 0.9rem; font-weight: 600; text-align: left;
}
.cat-toggle:hover { background: var(--surface-2); }
.cat-toggle .chev { transition: transform 0.18s ease; color: var(--muted); font-size: 0.7rem; flex: none; width: 12px; }
.cat-group.open .cat-toggle .chev { transform: rotate(90deg); }
.cat-toggle .cat-name { flex: 1 1 auto; min-width: 0; }
.cat-toggle .cat-count {
  flex: none; font-size: 0.72rem; font-weight: 500; color: var(--muted);
  background: var(--surface-2); border-radius: 999px; padding: 1px 8px;
}
.cat-group.open .cat-toggle .cat-count { background: var(--accent-soft); color: var(--accent); }

.cat-questions { list-style: none; margin: 0; padding: 0 0 4px; display: none; }
.cat-group.open .cat-questions { display: block; }
.q-link {
  display: flex; align-items: baseline; gap: 7px;
  padding: 6px 8px 6px 26px; margin: 1px 0;
  border-radius: var(--radius-sm); color: var(--ink); text-decoration: none;
  font-size: 0.84rem; line-height: 1.35;
}
.q-link:hover { background: var(--surface-2); text-decoration: none; }
.q-link.active { background: var(--accent-soft); color: var(--accent); font-weight: 600; }
.q-link .q-marks { flex: none; display: inline-flex; gap: 3px; width: 20px; }
.q-link .mark { font-size: 0.62rem; line-height: 1; }
.q-link .mark.visited { color: var(--ok); }
.q-link .mark.revealed { color: var(--accent); }
.q-link .q-title { flex: 1 1 auto; min-width: 0; }

/* ---------- main / topbar ---------- */
.main { min-width: 0; display: flex; flex-direction: column; }
.topbar {
  position: sticky; top: 0; z-index: 20;
  display: flex; align-items: center; gap: 12px;
  padding: 12px 24px;
  background: color-mix(in srgb, var(--bg) 88%, transparent);
  -webkit-backdrop-filter: blur(8px); backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--border);
}
.menu-btn {
  display: none; background: var(--surface); border: 1px solid var(--border);
  color: var(--ink); border-radius: var(--radius-sm); padding: 6px 10px; font-size: 1rem;
}
.brand-mini { font-family: var(--font-display); font-weight: 700; color: var(--ink); text-decoration: none; font-size: 0.98rem; white-space: nowrap; }
.brand-mini:hover { color: var(--accent); text-decoration: none; }

.search-wrap { position: relative; flex: 1 1 auto; max-width: 440px; margin: 0 auto; }
.search {
  width: 100%; background: var(--surface); color: var(--ink);
  border: 1px solid var(--border); border-radius: 999px;
  padding: 8px 14px 8px 34px; font-size: 0.88rem;
}
.search::placeholder { color: var(--muted); }
.search-wrap::before {
  content: "⌕"; position: absolute; left: 12px; top: 50%; transform: translateY(-50%);
  color: var(--muted); font-size: 1rem; pointer-events: none;
}
.search-results {
  position: absolute; top: calc(100% + 6px); left: 0; right: 0;
  background: var(--surface); border: 1px solid var(--border-strong);
  border-radius: var(--radius); box-shadow: var(--shadow-lg);
  max-height: 60vh; overflow-y: auto; z-index: 40; padding: 6px;
}
.search-results:empty, .search-results.hidden { display: none; }
.sr-item { display: block; padding: 8px 10px; border-radius: var(--radius-sm); text-decoration: none; color: var(--ink); }
.sr-item:hover, .sr-item.active { background: var(--accent-soft); text-decoration: none; }
.sr-title { font-weight: 600; font-size: 0.88rem; }
.sr-title mark { background: var(--accent-soft); color: var(--accent); border-radius: 3px; padding: 0 1px; }
.sr-cat { font-size: 0.74rem; color: var(--muted); }
.sr-empty { padding: 12px; color: var(--muted); font-size: 0.85rem; text-align: center; }

.topbar-actions { display: flex; gap: 6px; flex: none; }
.icon-btn {
  background: var(--surface); border: 1px solid var(--border); color: var(--ink);
  border-radius: var(--radius-sm); width: 36px; height: 36px;
  display: inline-flex; align-items: center; justify-content: center; font-size: 0.95rem;
}
.icon-btn:hover { border-color: var(--border-strong); }
.lang-btn { width: auto; padding: 0 12px; font-size: 0.8rem; font-weight: 600; }

/* ---------- reader ---------- */
.reader { width: 100%; max-width: var(--reader-max); margin: 0 auto; padding: 28px 24px 96px; }

/* ---------- overview ---------- */
.hero { margin-bottom: 24px; }
.hero .eyebrow { color: var(--accent); font-weight: 600; font-size: 0.78rem; letter-spacing: 0.06em; text-transform: uppercase; }
.hero h1 { font-size: 2rem; margin: 6px 0 10px; }
.hero .intro { color: var(--ink); font-size: 1.02rem; max-width: 66ch; }
.hero .source-note { color: var(--muted); font-size: 0.85rem; margin-top: 12px; }

.stats-row { display: flex; flex-wrap: wrap; gap: 10px; margin: 22px 0 26px; }
.stat {
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 12px 16px; min-width: 108px; flex: 1 1 auto;
}
.stat .num { font-family: var(--font-display); font-size: 1.5rem; font-weight: 700; color: var(--ink); }
.stat .lbl { font-size: 0.76rem; color: var(--muted); text-transform: uppercase; letter-spacing: 0.04em; }

.section-label { font-size: 0.78rem; font-weight: 600; text-transform: uppercase; letter-spacing: 0.06em; color: var(--muted); margin: 26px 0 12px; }

.cat-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(240px, 1fr)); gap: 14px; }
.cat-card {
  display: block; text-decoration: none; color: var(--ink);
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius-lg); padding: 18px; transition: border-color 0.18s ease, transform 0.18s ease;
}
.cat-card:hover { border-color: var(--accent); text-decoration: none; transform: translateY(-2px); }
.cat-card .cc-top { display: flex; align-items: center; justify-content: space-between; gap: 8px; }
.cat-card h3 { font-size: 1.06rem; margin: 0; }
.cat-card .cc-count { font-size: 0.74rem; color: var(--accent); background: var(--accent-soft); border-radius: 999px; padding: 2px 9px; font-weight: 600; flex: none; }
.cat-card .cc-blurb { color: var(--muted); font-size: 0.86rem; margin-top: 8px; line-height: 1.5; }
.cat-card .cc-prog { margin-top: 12px; height: 4px; background: var(--surface-2); border-radius: 999px; overflow: hidden; }
.cat-card .cc-prog > i { display: block; height: 100%; background: var(--ok); border-radius: 999px; }
.cat-card .cc-prog-lbl { font-size: 0.72rem; color: var(--muted); margin-top: 6px; }

.starts { display: flex; flex-direction: column; gap: 8px; }
.start-item {
  display: flex; gap: 10px; align-items: baseline; text-decoration: none; color: var(--ink);
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 12px 14px;
}
.start-item:hover { border-color: var(--accent); text-decoration: none; }
.start-item .si-title { font-weight: 600; }
.start-item .si-why { color: var(--muted); font-size: 0.84rem; }

/* ---------- question page ---------- */
.q-head { margin-bottom: 18px; }
.q-crumb { font-size: 0.78rem; color: var(--muted); margin-bottom: 6px; }
.q-crumb a { color: var(--muted); }
.q-crumb a:hover { color: var(--accent); }
.q-head h1 { font-size: 1.7rem; margin: 2px 0 0; }

.qcard {
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius-lg); padding: 20px 22px; margin-bottom: 16px;
}
.qcard > .qc-head { display: flex; align-items: center; gap: 10px; margin-bottom: 8px; }
.qc-badge {
  font-size: 0.7rem; font-weight: 700; letter-spacing: 0.05em; text-transform: uppercase;
  color: var(--accent); background: var(--accent-soft); border-radius: 999px; padding: 3px 10px;
}
.qc-head .qc-title { font-family: var(--font-display); font-weight: 600; font-size: 1.02rem; flex: 1 1 auto; }
.qc-ref {
  font-size: 0.72rem; color: var(--muted); font-family: var(--font-mono);
  border: 1px solid var(--border); border-radius: 999px; padding: 2px 8px; white-space: nowrap;
}
.qcard.rw { background: linear-gradient(180deg, var(--accent-soft), transparent), var(--surface); border-color: color-mix(in srgb, var(--accent) 30%, var(--border)); }
.rw-domain { font-size: 0.72rem; color: var(--muted); margin-top: 10px; font-style: italic; }

/* solution reveal */
.sol-veil { display: flex; flex-direction: column; align-items: flex-start; gap: 8px; }
.reveal-btn {
  background: var(--accent); color: var(--on-accent); border: none;
  border-radius: 999px; padding: 9px 18px; font-size: 0.88rem; font-weight: 600;
  display: inline-flex; align-items: center; gap: 8px;
}
.reveal-btn:hover { filter: brightness(1.04); }
.reveal-hint { font-size: 0.78rem; color: var(--muted); }
.sol-status {
  display: flex; gap: 8px; align-items: flex-start; padding: 12px 14px;
  background: var(--surface-2); border-radius: var(--radius); font-size: 0.88rem; color: var(--muted);
}
.sol-status .si { color: var(--warn); }

/* prev / next */
.q-nav { display: flex; gap: 10px; margin-top: 22px; }
.q-nav a {
  flex: 1 1 0; min-width: 0; text-decoration: none; color: var(--ink);
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 12px 14px; display: flex; flex-direction: column; gap: 2px;
}
.q-nav a:hover { border-color: var(--accent); text-decoration: none; }
.q-nav a.next { text-align: right; align-items: flex-end; }
.q-nav .qn-dir { font-size: 0.72rem; color: var(--muted); text-transform: uppercase; letter-spacing: 0.05em; }
.q-nav .qn-title { font-size: 0.9rem; font-weight: 600; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; max-width: 100%; }
.q-nav a.disabled { opacity: 0.4; pointer-events: none; }

/* ---------- typed blocks ---------- */
.blocks { font-size: 0.97rem; line-height: 1.68; }
.blocks > * { margin: 0 0 12px; }
.blocks > *:last-child { margin-bottom: 0; }
.blocks p { margin: 0 0 12px; }
.blocks ul { margin: 0 0 12px; padding-left: 22px; }
.blocks li { margin: 3px 0; }
.blocks code { background: var(--surface-2); border-radius: 4px; padding: 1px 5px; font-size: 0.88em; }
.blocks pre {
  background: var(--surface-2); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 12px 14px; overflow-x: auto; font-size: 0.85rem; line-height: 1.5;
}
.blocks pre code { background: none; padding: 0; }

.def-block {
  border-left: 3px solid var(--accent); background: var(--accent-soft);
  border-radius: 0 var(--radius) var(--radius) 0; padding: 10px 14px;
}
.def-block .def-term { font-family: var(--font-display); font-weight: 700; }
.def-block .def-plain { color: var(--muted); font-size: 0.86rem; margin-top: 4px; }

.formula-block { overflow-x: auto; padding: 6px 0; }
.formula-block .katex-display { margin: 0; }
.formula-fallback {
  display: block; background: var(--surface-2); border: 1px solid var(--border);
  border-radius: var(--radius-sm); padding: 8px 12px; font-family: var(--font-mono);
  font-size: 0.85rem; overflow-x: auto; white-space: pre;
}
.formula-note { font-size: 0.78rem; color: var(--muted); margin-top: 4px; }
.inline-fallback { font-family: var(--font-mono); font-size: 0.9em; background: var(--surface-2); border-radius: 4px; padding: 0 4px; }

figure.fig-block { margin: 0; }
figure.fig-block img { max-width: 100%; height: auto; border: 1px solid var(--border); border-radius: var(--radius-sm); background: #fff; }
figure.fig-block figcaption { font-size: 0.8rem; color: var(--muted); margin-top: 6px; }

.callout {
  border-radius: var(--radius); padding: 12px 14px 12px 42px; position: relative;
  border: 1px solid var(--border);
}
.callout::before { position: absolute; left: 14px; top: 12px; font-size: 1rem; }
.callout.intuition { background: var(--accent-soft); border-color: color-mix(in srgb, var(--accent) 24%, var(--border)); }
.callout.intuition::before { content: "💡"; }
.callout.warning { background: color-mix(in srgb, var(--warn) 12%, var(--surface)); }
.callout.warning::before { content: "⚠️"; }
.callout.example { background: var(--surface-2); }
.callout.example::before { content: "🔎"; }

.table-wrap { overflow-x: auto; }
.blocks table { border-collapse: collapse; width: 100%; font-size: 0.88rem; }
.blocks th, .blocks td { border: 1px solid var(--border); padding: 7px 10px; text-align: left; vertical-align: top; }
.blocks thead th { background: var(--surface-2); font-family: var(--font-display); }

.quote-block { border-left: 3px solid var(--border-strong); padding: 4px 0 4px 14px; color: var(--muted); font-style: italic; }
.quote-block .quote-ref { display: block; font-style: normal; font-size: 0.76rem; margin-top: 4px; }

/* ---------- misc ---------- */
.loading, .empty-state { color: var(--muted); padding: 40px 0; text-align: center; }
.scrim { display: none; }

/* ---------- responsive ---------- */
@media (max-width: 1000px) {
  .layout { grid-template-columns: 1fr; }
  .sidebar {
    position: fixed; top: 0; left: 0; width: min(86vw, var(--sidebar-w)); z-index: 60;
    transform: translateX(-100%); transition: transform 0.24s ease;
    box-shadow: var(--shadow-lg);
  }
  body.drawer-open .sidebar { transform: translateX(0); }
  body.drawer-open .scrim {
    display: block; position: fixed; inset: 0; z-index: 50;
    background: rgba(20, 20, 19, 0.4);
  }
  .menu-btn { display: inline-flex; }
  .search-wrap { margin: 0; }
  .reader { padding: 22px 18px 96px; }
  .hero h1 { font-size: 1.7rem; }
}
@media (max-width: 560px) {
  .topbar { padding: 10px 14px; gap: 8px; }
  .brand-mini { display: none; }
  .qcard { padding: 16px; }
  .q-nav { flex-direction: column; }
  .stats-row .stat { min-width: calc(50% - 5px); }
}

/* ---------- motion / print ---------- */
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { animation-duration: 0.001ms !important; transition-duration: 0.001ms !important; }
}
@media print {
  .sidebar, .topbar, .q-nav, .scrim, .buddy-fab, .buddy-panel { display: none !important; }
  .layout { display: block; }
  .reader { max-width: none; padding: 0; }
  .qcard { border: 1px solid #ccc; break-inside: avoid; }
  .sol-veil, .reveal-btn { display: none !important; }
  body { background: #fff; }
}