/* ===== Quant Research 知识库 — shared styles ===== */
:root {
  --accent: #f97316;
  --accent-soft: #fdba74;
  --accent-weak: rgba(249, 115, 22, 0.12);
  --bg: #ffffff;
  --bg-alt: #f7f8fa;
  --bg-code: #f4f5f7;
  --surface: #ffffff;
  --border: #e6e8eb;
  --border-strong: #d6d9de;
  --text: #1f2328;
  --text-soft: #57606a;
  --text-faint: #8b949e;
  --link: #b45309;
  --shadow: 0 1px 3px rgba(16, 24, 40, 0.06), 0 1px 2px rgba(16, 24, 40, 0.04);
  --shadow-lg: 0 12px 32px rgba(16, 24, 40, 0.12);
  --radius: 12px;
  --radius-sm: 8px;
  --sidebar-w: 290px;
  --toc-w: 220px;
  --topbar-h: 58px;
  --maxw: 860px;
  --content-gap: 180px;
  --mono: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas, "Liberation Mono", monospace;
  --sans: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Helvetica Neue", Arial, sans-serif;
}
html[data-theme="dark"] {
  --accent: #fb923c;
  --accent-soft: #c2410c;
  --accent-weak: rgba(251, 146, 60, 0.16);
  --bg: #0d1117;
  --bg-alt: #11161d;
  --bg-code: #161b22;
  --surface: #11161d;
  --border: #21262d;
  --border-strong: #30363d;
  --text: #e6edf3;
  --text-soft: #9da7b3;
  --text-faint: #6e7681;
  --link: #fdba74;
  --shadow: 0 1px 3px rgba(0, 0, 0, 0.4);
  --shadow-lg: 0 12px 32px rgba(0, 0, 0, 0.5);
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; scroll-padding-top: calc(var(--topbar-h) + 16px); }
body {
  margin: 0;
  font-family: var(--sans);
  background: var(--bg);
  color: var(--text);
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
  font-size: 16px;
}

/* ===== Topbar ===== */
.topbar {
  position: fixed; top: 0; left: 0; right: 0; height: var(--topbar-h);
  display: flex; align-items: center; gap: 14px;
  padding: 0 18px;
  background: color-mix(in srgb, var(--bg) 88%, transparent);
  backdrop-filter: saturate(160%) blur(10px);
  border-bottom: 1px solid var(--border);
  z-index: 100;
}
.topbar .brand { display: flex; align-items: center; gap: 10px; text-decoration: none; color: var(--text); font-weight: 700; }
.topbar .brand img { width: 28px; height: 28px; }
.topbar .brand span { font-size: 15px; letter-spacing: -0.01em; }
.topbar .brand small { color: var(--text-faint); font-weight: 500; font-size: 12px; margin-left: 2px; }
.topbar .spacer { flex: 1; }
.topbar .icon-btn {
  display: inline-flex; align-items: center; justify-content: center;
  width: 36px; height: 36px; border-radius: 9px; cursor: pointer;
  background: transparent; border: 1px solid transparent; color: var(--text-soft);
  font-size: 17px; transition: background .15s, color .15s;
}
.topbar .icon-btn:hover { background: var(--bg-alt); color: var(--text); }
.menu-toggle { display: none; }

/* search box in topbar */
.search-wrap { position: relative; }
#search-input {
  width: 230px; max-width: 42vw; height: 36px; padding: 0 12px 0 34px;
  border: 1px solid var(--border-strong); border-radius: 9px;
  background: var(--bg-alt) url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='15' height='15' fill='none' stroke='%238b949e' stroke-width='2' viewBox='0 0 24 24'%3E%3Ccircle cx='11' cy='11' r='7'/%3E%3Cpath d='m21 21-4.3-4.3'/%3E%3C/svg%3E") no-repeat 11px center;
  color: var(--text); font-size: 14px; font-family: var(--sans); transition: border-color .15s, box-shadow .15s;
}
#search-input:focus { outline: none; border-color: var(--accent); box-shadow: 0 0 0 3px var(--accent-weak); }
#search-results {
  position: absolute; top: 44px; right: 0; width: 420px; max-width: 86vw;
  max-height: 60vh; overflow-y: auto; background: var(--surface);
  border: 1px solid var(--border-strong); border-radius: var(--radius);
  box-shadow: var(--shadow-lg); padding: 6px; display: none; z-index: 200;
}
#search-results.show { display: block; }
#search-results a {
  display: block; padding: 9px 12px; border-radius: var(--radius-sm);
  text-decoration: none; color: var(--text); transition: background .12s;
}
#search-results a:hover, #search-results a.active { background: var(--accent-weak); }
#search-results .sr-title { font-weight: 600; font-size: 14px; }
#search-results .sr-meta { font-size: 12px; color: var(--text-faint); margin-top: 2px; }
#search-results .sr-empty { padding: 16px; color: var(--text-faint); text-align: center; font-size: 14px; }
#search-results mark { background: var(--accent-soft); color: #1f2328; border-radius: 3px; padding: 0 2px; }

/* ===== Layout ===== */
.layout { display: flex; padding-top: var(--topbar-h); padding-left: var(--sidebar-w); min-height: 100vh; }

/* ===== Sidebar ===== */
.sidebar {
  position: fixed; top: var(--topbar-h); bottom: 0; left: 0; width: var(--sidebar-w);
  overflow-y: auto; padding: 22px 14px 60px; border-right: 1px solid var(--border);
  background: var(--bg-alt);
}
.sidebar .nav-group { margin-bottom: 20px; }
.sidebar .nav-group > .nav-group-title {
  font-size: 12px; font-weight: 700; text-transform: uppercase; letter-spacing: 0.06em;
  color: var(--text-faint); padding: 4px 12px; margin-bottom: 4px;
}
.sidebar a.nav-link {
  display: block; padding: 7px 12px; border-radius: var(--radius-sm);
  text-decoration: none; color: var(--text-soft); font-size: 14.5px;
  transition: background .12s, color .12s; line-height: 1.4;
}
.sidebar a.nav-link:hover { background: var(--accent-weak); color: var(--text); }
.sidebar a.nav-link.active { background: var(--accent-weak); color: var(--link); font-weight: 600; }
.sidebar a.nav-link .nl-emoji { margin-right: 7px; }

/* ===== Content ===== */
.content {
  flex: 1; min-width: 0; max-width: var(--maxw);
  margin: 0 0 0 var(--content-gap); padding: 40px 48px 120px;
}
.content.has-toc { margin-right: 0; }
.content h1 {
  font-size: 32px; line-height: 1.25; margin: 0 0 8px; letter-spacing: -0.02em;
}
.content .page-lead { color: var(--text-soft); font-size: 16.5px; margin: 0 0 28px; }
.content h2 {
  font-size: 24px; margin: 48px 0 14px; padding-bottom: 8px;
  border-bottom: 1px solid var(--border); letter-spacing: -0.01em; scroll-margin-top: 76px;
}
.content h3 { font-size: 19px; margin: 32px 0 10px; scroll-margin-top: 76px; }
.content h4 { font-size: 16px; margin: 22px 0 8px; color: var(--text-soft); scroll-margin-top: 76px; }
.content p { margin: 12px 0; }
.content a { color: var(--link); text-decoration: none; border-bottom: 1px solid transparent; }
.content a:hover { border-bottom-color: var(--link); }
.content ul, .content ol { padding-left: 24px; }
.content li { margin: 5px 0; }
.content strong { color: var(--text); font-weight: 700; }
.content hr { border: none; border-top: 1px solid var(--border); margin: 36px 0; }

/* inline + block code */
.content code {
  font-family: var(--mono); font-size: 0.88em; background: var(--bg-code);
  padding: 2px 6px; border-radius: 5px; border: 1px solid var(--border);
}
.content pre {
  background: var(--bg-code); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 16px 18px; overflow-x: auto; margin: 16px 0; line-height: 1.55;
}
.content pre code { background: none; border: none; padding: 0; font-size: 13.5px; }

/* tables */
.content table {
  width: 100%; border-collapse: collapse; margin: 18px 0; font-size: 14.5px;
  border: 1px solid var(--border); border-radius: var(--radius); overflow: hidden;
}
.content th, .content td { padding: 10px 14px; text-align: left; border-bottom: 1px solid var(--border); vertical-align: top; }
.content th { background: var(--bg-alt); font-weight: 700; font-size: 13.5px; }
.content tr:last-child td { border-bottom: none; }
.content tbody tr:hover { background: var(--accent-weak); }

/* KaTeX scroll on overflow */
.katex-display { overflow-x: auto; overflow-y: hidden; padding: 4px 0; }

/* ===== Reusable components for content authors ===== */
/* Q&A card */
.qa-card {
  border: 1px solid var(--border); border-radius: var(--radius);
  background: var(--surface); box-shadow: var(--shadow);
  margin: 24px 0; overflow: hidden; scroll-margin-top: 76px;
}
.qa-card > .qa-q {
  display: flex; align-items: flex-start; gap: 12px; padding: 16px 20px;
  background: var(--bg-alt); border-bottom: 1px solid var(--border);
  font-weight: 700; font-size: 17px; line-height: 1.45;
}
.qa-card > .qa-q .qa-id {
  flex: none; font-family: var(--mono); font-size: 13px; font-weight: 700;
  color: #fff; background: var(--accent); padding: 2px 9px; border-radius: 999px; margin-top: 2px;
}
.qa-card > .qa-body { padding: 18px 22px 6px; }
.qa-card > .qa-body > h4:first-child { margin-top: 4px; }

/* callout boxes */
.callout {
  border-left: 4px solid var(--accent); background: var(--accent-weak);
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0; padding: 12px 18px; margin: 16px 0;
}
.callout .callout-title { font-weight: 700; margin-bottom: 4px; display: flex; align-items: center; gap: 7px; }
.callout.tip { border-left-color: #16a34a; background: rgba(22,163,74,0.10); }
.callout.warn { border-left-color: #dc2626; background: rgba(220,38,38,0.10); }
.callout.note { border-left-color: #2563eb; background: rgba(37,99,235,0.10); }
.callout.deep { border-left-color: #7c3aed; background: rgba(124,58,237,0.10); }
.callout.eli5 { border-left-color: #16a34a; background: rgba(22,163,74,0.13); }
.callout.eli5 .callout-title { color: #15803d; }
html[data-theme="dark"] .callout.eli5 .callout-title { color: #4ade80; }
.callout p:first-child { margin-top: 0; }
.callout p:last-child { margin-bottom: 0; }

/* "深度拓展" expandable */
details.expand {
  border: 1px solid var(--border); border-radius: var(--radius); margin: 16px 0;
  background: var(--surface); overflow: hidden;
}
details.expand > summary {
  cursor: pointer; padding: 13px 18px; font-weight: 600; list-style: none;
  display: flex; align-items: center; gap: 9px; background: var(--bg-alt);
}
details.expand > summary::-webkit-details-marker { display: none; }
details.expand > summary::before { content: "▸"; color: var(--accent); transition: transform .15s; }
details.expand[open] > summary::before { transform: rotate(90deg); }
details.expand[open] > summary { border-bottom: 1px solid var(--border); }
details.expand .expand-body { padding: 6px 20px 14px; }

/* tag / pill */
.pill {
  display: inline-block; font-size: 12px; font-weight: 600; padding: 2px 10px;
  border-radius: 999px; background: var(--accent-weak); color: var(--link); margin: 2px 4px 2px 0;
}
.star { color: var(--accent); font-weight: 700; }

/* card grid (home, resources) */
.card-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(240px, 1fr)); gap: 16px; margin: 20px 0; }
.card {
  border: 1px solid var(--border); border-radius: var(--radius); padding: 18px 20px;
  background: var(--surface); box-shadow: var(--shadow); text-decoration: none; color: var(--text);
  transition: transform .15s, box-shadow .15s, border-color .15s; display: block;
}
a.card:hover { transform: translateY(-2px); box-shadow: var(--shadow-lg); border-color: var(--accent-soft); }
.card .card-emoji { font-size: 24px; }
.card .card-title { font-weight: 700; font-size: 16.5px; margin: 8px 0 4px; }
.card .card-desc { color: var(--text-soft); font-size: 14px; line-height: 1.55; }

/* on-page TOC */
.toc {
  position: fixed; top: calc(var(--topbar-h) + 30px);
  left: calc(var(--sidebar-w) + var(--content-gap) + var(--maxw) + 44px); right: auto;
  width: var(--toc-w); max-height: calc(100vh - var(--topbar-h) - 60px); overflow-y: auto;
  font-size: 13px; padding-left: 14px; border-left: 1px solid var(--border);
}
.toc .toc-title { font-weight: 700; color: var(--text-faint); text-transform: uppercase; font-size: 11px; letter-spacing: 0.06em; margin-bottom: 8px; }
.toc a { display: block; padding: 3px 0; color: var(--text-soft); text-decoration: none; line-height: 1.4; border-left: 2px solid transparent; padding-left: 10px; margin-left: -12px; }
.toc a:hover { color: var(--text); }
.toc a.active { color: var(--link); border-left-color: var(--accent); font-weight: 600; }
.toc a.lvl-3 { padding-left: 22px; font-size: 12.5px; }

/* breadcrumb / prev-next */
.page-nav { display: flex; justify-content: space-between; gap: 16px; margin-top: 60px; padding-top: 24px; border-top: 1px solid var(--border); }
.page-nav a {
  flex: 1; border: 1px solid var(--border); border-radius: var(--radius); padding: 14px 18px;
  text-decoration: none; color: var(--text); transition: border-color .15s, background .15s;
}
.page-nav a:hover { border-color: var(--accent-soft); background: var(--bg-alt); }
.page-nav .pn-dir { font-size: 12px; color: var(--text-faint); }
.page-nav .pn-title { font-weight: 600; margin-top: 2px; }
.page-nav a.next { text-align: right; }

/* hero (home) */
.hero { text-align: center; padding: 30px 0 18px; }
.hero img { width: 72px; height: 72px; }
.hero h1 { font-size: 38px; margin: 14px 0 8px; letter-spacing: -0.02em; }
.hero p { color: var(--text-soft); font-size: 17px; max-width: 640px; margin: 0 auto; }
.hero .hero-actions { margin-top: 24px; display: flex; gap: 12px; justify-content: center; flex-wrap: wrap; }
.btn {
  display: inline-flex; align-items: center; gap: 8px; padding: 11px 22px; border-radius: 10px;
  font-weight: 600; text-decoration: none; font-size: 15px; border: 1px solid var(--border-strong);
  color: var(--text); background: var(--surface); transition: transform .12s, box-shadow .12s;
}
.btn:hover { transform: translateY(-1px); box-shadow: var(--shadow); }
.btn.primary { background: var(--accent); border-color: var(--accent); color: #fff; }

.backdrop { display: none; }

/* ===== Responsive ===== */
@media (max-width: 1619px) {
  /* not enough room for sidebar + content + right-hand TOC side by side */
  .toc { display: none; }
}
@media (max-width: 900px) {
  :root { --sidebar-w: 280px; }
  .layout { padding-left: 0; }
  .menu-toggle { display: inline-flex; }
  .sidebar {
    transform: translateX(-100%); transition: transform .22s ease; z-index: 90;
    box-shadow: var(--shadow-lg);
  }
  body.nav-open .sidebar { transform: translateX(0); }
  body.nav-open .backdrop { display: block; position: fixed; inset: var(--topbar-h) 0 0 0; background: rgba(0,0,0,0.4); z-index: 80; }
  .content { padding: 28px 20px 100px; margin-left: 0; }
  .content h1 { font-size: 27px; }
  #search-input { width: 150px; }
}