:root {
  --bg: #ffffff;
  --bg-soft: #f7f8fa;
  --bg-code: #f6f8fa;
  --sidebar-bg: #fafbfc;
  --border: #e5e7eb;
  --border-soft: #eef0f3;
  --text: #1f2328;
  --text-soft: #57606a;
  --text-mute: #8b949e;
  --accent: #111827;
  --link: #0969da;
  --link-hover: #0550ae;
  --active-bg: #eef2ff;
  --active-text: #1e3a8a;
  --shadow: 0 1px 3px rgba(0,0,0,.06), 0 8px 24px rgba(0,0,0,.04);
  --radius: 10px;
  --sidebar-w: 300px;
  --content-max: 820px;
  --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", Roboto, Helvetica, Arial, sans-serif;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  font-family: var(--sans);
  color: var(--text);
  background: var(--bg);
  -webkit-font-smoothing: antialiased;
  line-height: 1.7;
}

/* ---------- Sidebar ---------- */
.sidebar {
  position: fixed;
  top: 0; left: 0; bottom: 0;
  width: var(--sidebar-w);
  background: var(--sidebar-bg);
  border-right: 1px solid var(--border);
  display: flex;
  flex-direction: column;
  z-index: 40;
}
.brand {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 20px 20px 16px;
  border-bottom: 1px solid var(--border-soft);
}
.brand-logo {
  width: 38px; height: 38px;
  display: flex; align-items: center; justify-content: center;
  background: #111827; color: #fff;
  border-radius: 9px; font-size: 18px; font-weight: 700;
}
.brand-title { font-weight: 700; font-size: 15px; }
.brand-sub { font-size: 11.5px; color: var(--text-mute); margin-top: 2px; }

.search-box { padding: 14px 16px 8px; position: relative; }
#searchInput {
  width: 100%;
  padding: 9px 12px;
  border: 1px solid var(--border);
  border-radius: 8px;
  font-size: 13px;
  background: #fff;
  outline: none;
  transition: border-color .15s, box-shadow .15s;
}
#searchInput:focus { border-color: #93c5fd; box-shadow: 0 0 0 3px rgba(59,130,246,.12); }
.search-results {
  position: absolute;
  left: 16px; right: 16px; top: 100%;
  background: #fff;
  border: 1px solid var(--border);
  border-radius: 8px;
  box-shadow: var(--shadow);
  max-height: 320px; overflow-y: auto;
  z-index: 60; display: none;
}
.search-results.show { display: block; }
.search-result-item {
  padding: 9px 12px; font-size: 13px; cursor: pointer;
  border-bottom: 1px solid var(--border-soft);
}
.search-result-item:last-child { border-bottom: none; }
.search-result-item:hover, .search-result-item.active { background: var(--active-bg); }
.search-result-item .sr-group { font-size: 11px; color: var(--text-mute); }
.search-result-empty { padding: 12px; font-size: 13px; color: var(--text-mute); }

.nav { flex: 1; overflow-y: auto; padding: 8px 10px 20px; }
.nav-group-title {
  font-size: 11px; font-weight: 700; letter-spacing: .06em;
  text-transform: uppercase; color: var(--text-mute);
  padding: 16px 12px 6px;
}
.nav-item {
  display: block;
  padding: 7px 12px;
  font-size: 13.5px;
  color: var(--text-soft);
  text-decoration: none;
  border-radius: 7px;
  cursor: pointer;
  transition: background .12s, color .12s;
}
.nav-item:hover { background: #eef0f3; color: var(--text); }
.nav-item.active { background: var(--active-bg); color: var(--active-text); font-weight: 600; }
.sidebar-footer {
  padding: 12px 16px; font-size: 11px; color: var(--text-mute);
  border-top: 1px solid var(--border-soft);
}

/* ---------- Main ---------- */
.main {
  margin-left: var(--sidebar-w);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}
.topbar {
  position: sticky; top: 0; z-index: 20;
  height: 4px; background: transparent;
}
.topbar-progress { height: 4px; width: 100%; background: transparent; }
.topbar-progress-bar { height: 100%; width: 0; background: linear-gradient(90deg,#111827,#4b5563); transition: width .1s; }

.content {
  width: 100%;
  max-width: var(--content-max);
  margin: 0 auto;
  padding: 44px 40px 40px;
  flex: 1;
}
.loading { color: var(--text-mute); padding: 40px 0; }

/* ---------- Markdown typography ---------- */
.content h1 {
  font-size: 32px; font-weight: 800; line-height: 1.25;
  margin: 0 0 8px; letter-spacing: -.02em;
}
.content > p:first-of-type { color: var(--text-soft); font-size: 16px; }
.content h2 {
  font-size: 23px; font-weight: 700; margin: 42px 0 14px;
  padding-bottom: 8px; border-bottom: 1px solid var(--border-soft);
  scroll-margin-top: 24px;
}
.content h3 { font-size: 18px; font-weight: 700; margin: 30px 0 10px; scroll-margin-top: 24px; }
.content h4 { font-size: 15px; font-weight: 700; margin: 22px 0 8px; }
.content p { margin: 12px 0; }
.content a { color: var(--link); text-decoration: none; }
.content a:hover { color: var(--link-hover); text-decoration: underline; }
.content ul, .content ol { padding-left: 26px; margin: 12px 0; }
.content li { margin: 5px 0; }
.content strong { font-weight: 700; color: var(--text); }
.content hr { border: none; border-top: 1px solid var(--border-soft); margin: 32px 0; }
.content blockquote {
  margin: 16px 0; padding: 2px 18px;
  border-left: 4px solid #d0d7de; color: var(--text-soft);
  background: var(--bg-soft); border-radius: 0 8px 8px 0;
}
.content blockquote p { margin: 10px 0; }

/* inline code */
.content code {
  font-family: var(--mono);
  font-size: 85%;
  background: rgba(175,184,193,.2);
  padding: .2em .4em; border-radius: 6px;
}
/* code block */
.content pre {
  position: relative;
  background: var(--bg-code);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 16px 16px;
  overflow-x: auto;
  margin: 16px 0;
  font-size: 13.5px;
  line-height: 1.6;
}
.content pre code {
  background: none; padding: 0; font-size: 13.5px; border-radius: 0;
  font-family: var(--mono);
}
.code-header {
  display: flex; align-items: center; justify-content: space-between;
  background: #eff1f4; border: 1px solid var(--border); border-bottom: none;
  border-radius: var(--radius) var(--radius) 0 0;
  padding: 7px 14px; font-size: 12px; color: var(--text-soft);
  font-family: var(--mono);
}
.code-header + pre { border-top-left-radius: 0; border-top-right-radius: 0; margin-top: 0; }
.copy-btn {
  border: 1px solid var(--border); background: #fff;
  color: var(--text-soft); font-size: 11.5px;
  padding: 3px 10px; border-radius: 6px; cursor: pointer;
  transition: all .12s;
}
.copy-btn:hover { background: var(--active-bg); color: var(--active-text); border-color: #bfdbfe; }
.copy-btn.copied { background: #dcfce7; color: #166534; border-color: #bbf7d0; }

/* tables */
.content table {
  border-collapse: collapse; width: 100%; margin: 16px 0; font-size: 14px;
  display: block; overflow-x: auto;
}
.content th, .content td { border: 1px solid var(--border); padding: 8px 12px; text-align: left; }
.content th { background: var(--bg-soft); font-weight: 700; }
.content tr:nth-child(even) td { background: #fbfcfd; }

/* callouts via blockquote first word */
.callout { border-radius: 10px; padding: 14px 18px; margin: 16px 0; border: 1px solid; }
.callout-tip { background: #f0fdf4; border-color: #bbf7d0; }
.callout-warn { background: #fffbeb; border-color: #fde68a; }
.callout-note { background: #eff6ff; border-color: #bfdbfe; }

/* ---------- Pager ---------- */
.pager {
  max-width: var(--content-max);
  margin: 0 auto; width: 100%;
  padding: 0 40px 20px;
  display: flex; gap: 14px; justify-content: space-between;
}
.pager-link {
  flex: 1; border: 1px solid var(--border); border-radius: var(--radius);
  padding: 14px 18px; text-decoration: none; color: var(--text);
  transition: border-color .12s, box-shadow .12s; background: #fff;
}
.pager-link:hover { border-color: #93c5fd; box-shadow: var(--shadow); }
.pager-link.next { text-align: right; }
.pager-dir { font-size: 12px; color: var(--text-mute); }
.pager-title { font-weight: 700; font-size: 15px; margin-top: 3px; }
.pager-link.empty { visibility: hidden; }

.page-footer {
  max-width: var(--content-max); margin: 0 auto; width: 100%;
  padding: 24px 40px 60px; color: var(--text-mute); font-size: 13px;
  border-top: 1px solid var(--border-soft);
}

/* ---------- Mobile ---------- */
.menu-toggle {
  display: none;
  position: fixed; top: 12px; left: 12px; z-index: 50;
  width: 40px; height: 40px; border-radius: 9px;
  border: 1px solid var(--border); background: #fff;
  font-size: 18px; cursor: pointer; box-shadow: var(--shadow);
}
.overlay {
  display: none; position: fixed; inset: 0;
  background: rgba(0,0,0,.35); z-index: 35;
}
.overlay.show { display: block; }

@media (max-width: 900px) {
  .menu-toggle { display: block; }
  .sidebar { transform: translateX(-100%); transition: transform .25s; box-shadow: var(--shadow); }
  .sidebar.open { transform: translateX(0); }
  .main { margin-left: 0; }
  .content, .pager, .page-footer { padding-left: 20px; padding-right: 20px; }
  .content { padding-top: 64px; }
  .pager { flex-direction: column; }
}