:root {
  --bg: #f6f7fb;
  --paper: #ffffff;
  --paper-soft: #f9fbff;
  --text: #172033;
  --muted: #687386;
  --border: #dfe6f0;
  --primary: #1f6feb;
  --primary-soft: #eaf2ff;
  --accent: #0f9f8f;
  --warning: #b45309;
  --code-bg: #0f172a;
  --code-text: #e5edf8;
  --shadow: 0 20px 50px rgba(29, 45, 70, .08);
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: Inter, ui-sans-serif, -apple-system, BlinkMacSystemFont, "Segoe UI", "Noto Sans SC", "PingFang SC", "Microsoft YaHei", sans-serif;
  line-height: 1.75;
  letter-spacing: 0;
}
a { color: inherit; text-decoration: none; }
.site-header {
  position: sticky; top: 0; z-index: 20;
  display: flex; align-items: center; justify-content: space-between;
  padding: 14px 28px;
  background: rgba(255,255,255,.88);
  backdrop-filter: blur(16px);
  border-bottom: 1px solid var(--border);
}
.brand { font-weight: 800; font-size: 20px; color: var(--primary); }
.top-nav { display: flex; gap: 18px; font-size: 14px; color: var(--muted); }
.top-nav a:hover { color: var(--primary); }
.home-hero, .series-landing {
  max-width: 980px;
  margin: 56px auto;
  padding: 0 24px;
}
.home-hero h1, .series-landing h1 {
  margin: 8px 0 16px;
  font-size: clamp(34px, 5vw, 58px);
  line-height: 1.08;
  letter-spacing: 0;
}
.home-hero p, .series-description { max-width: 720px; color: var(--muted); font-size: 18px; }
.eyebrow {
  margin: 0;
  color: var(--accent);
  font-weight: 800;
  text-transform: uppercase;
  font-size: 13px;
}
.button, .series-card, .chapter-row {
  border: 1px solid var(--border);
  background: var(--paper);
  border-radius: 8px;
  box-shadow: var(--shadow);
}
.button { display: inline-flex; padding: 10px 16px; margin-top: 12px; font-weight: 700; }
.button.primary { background: var(--primary); color: white; border-color: var(--primary); }
.home-section { max-width: 980px; margin: 0 auto 80px; padding: 0 24px; }
.series-card-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(260px, 1fr)); gap: 18px; }
.series-card { display: block; padding: 22px; }
.series-card:hover, .chapter-row:hover { transform: translateY(-1px); border-color: #b8cef3; }
.card-label { color: var(--accent); font-size: 13px; font-weight: 800; }
.series-card h3 { margin: 8px 0; font-size: 22px; }
.series-card p { color: var(--muted); margin: 0; }
.chapter-list { display: grid; gap: 12px; margin-top: 28px; }
.chapter-row { display: flex; gap: 16px; align-items: center; padding: 16px 18px; }
.chapter-number { color: var(--primary); font-weight: 900; font-size: 20px; }
.chapter-row em { display: block; color: var(--muted); font-style: normal; font-size: 14px; margin-top: 2px; }
.doc-shell {
  display: grid;
  grid-template-columns: minmax(220px, 270px) minmax(0, 820px) minmax(210px, 260px);
  gap: 28px;
  max-width: 1440px;
  margin: 0 auto;
  padding: 28px;
}
.series-sidebar, .toc-sidebar { position: sticky; top: 76px; align-self: start; max-height: calc(100vh - 92px); overflow: auto; }
.series-sidebar {
  padding: 18px;
  background: var(--paper);
  border: 1px solid var(--border);
  border-radius: 8px;
}
.back-link { color: var(--primary); font-size: 14px; font-weight: 700; }
.series-sidebar h2 { font-size: 16px; line-height: 1.35; margin: 14px 0; }
.series-sidebar nav { display: grid; gap: 6px; }
.series-sidebar nav a {
  display: grid; grid-template-columns: 34px 1fr; gap: 8px; align-items: start;
  padding: 9px 10px;
  color: var(--muted);
  border-radius: 8px;
  font-size: 14px;
  line-height: 1.35;
}
.series-sidebar nav a span { color: #94a3b8; font-weight: 800; }
.series-sidebar nav a.active, .series-sidebar nav a:hover { background: var(--primary-soft); color: var(--primary); }
.article {
  background: var(--paper);
  border: 1px solid var(--border);
  border-radius: 8px;
  box-shadow: var(--shadow);
  overflow: hidden;
}
.article-header { padding: 44px 52px 20px; border-bottom: 1px solid var(--border); background: linear-gradient(180deg, #fff, #f8fbff); }
.article-header h1 { margin: 8px 0 10px; font-size: clamp(30px, 4vw, 46px); line-height: 1.15; }
.summary { color: var(--muted); margin: 0; font-size: 17px; }
.content { padding: 22px 52px 48px; font-size: 17px; }
.content h2 { margin-top: 42px; padding-top: 8px; font-size: 26px; line-height: 1.25; }
.content h2::before { content: ""; display: inline-block; width: 6px; height: 22px; margin-right: 10px; border-radius: 4px; background: var(--primary); vertical-align: -4px; }
.content h3 { margin-top: 30px; font-size: 21px; }
.content p { margin: 14px 0; }
.content strong { color: var(--primary); }
.content code:not(pre code) { padding: 2px 6px; border-radius: 6px; background: var(--primary-soft); color: #0f4aa8; font-size: .92em; }
.content pre { overflow-x: auto; padding: 18px 20px; border-radius: 8px; background: var(--code-bg); color: var(--code-text); line-height: 1.65; }
.content pre code { color: inherit; background: transparent; padding: 0; }
.content blockquote { margin: 20px 0; padding: 12px 18px; border-left: 4px solid var(--accent); background: #eefcf8; color: #145a52; }
.content table { width: 100%; border-collapse: collapse; margin: 20px 0; font-size: 15px; overflow: hidden; border-radius: 8px; }
.content th, .content td { border: 1px solid var(--border); padding: 10px 12px; text-align: left; }
.content th { background: #eef4ff; color: #173b73; }
.content img { display: block; max-width: 100%; margin: 24px auto; border-radius: 8px; border: 1px solid var(--border); background: #fff; }
.content ul, .content ol { padding-left: 1.35em; }
.content li::marker { color: var(--primary); }
.toc-box { padding: 16px; background: var(--paper); border: 1px solid var(--border); border-radius: 8px; font-size: 14px; }
.toc-box strong { display: block; margin-bottom: 8px; color: var(--text); }
.toc-box nav ul { list-style: none; padding-left: 0; margin: 0; }
.toc-box nav ul ul { padding-left: 12px; margin-top: 4px; }
.toc-box a { display: block; padding: 4px 0; color: var(--muted); line-height: 1.35; }
.toc-box a:hover { color: var(--primary); }
.article-pager { display: flex; justify-content: space-between; gap: 14px; padding: 22px 52px; border-top: 1px solid var(--border); background: var(--paper-soft); }
.article-pager a { color: var(--primary); font-weight: 800; }
.site-footer { display: flex; justify-content: center; gap: 16px; padding: 30px; color: var(--muted); font-size: 14px; }
@media (max-width: 1120px) {
  .doc-shell { grid-template-columns: 1fr; padding: 18px; }
  .series-sidebar, .toc-sidebar { position: static; max-height: none; }
  .toc-sidebar { display: none; }
}
@media (max-width: 680px) {
  .site-header { padding: 12px 16px; align-items: flex-start; gap: 8px; flex-direction: column; }
  .top-nav { flex-wrap: wrap; gap: 10px; }
  .article-header, .content, .article-pager { padding-left: 22px; padding-right: 22px; }
  .content { font-size: 16px; }
  .site-footer { flex-direction: column; text-align: center; }
}