:root {
  --bg: #f8fafc; --bg-card: #ffffff; --text: #1e293b; --text-secondary: #64748b;
  --text-muted: #94a3b8; --accent: #6366f1; --accent-light: #818cf8;
  --accent-bg: rgba(99,102,241,0.08); --accent-bg-hover: rgba(99,102,241,0.14);
  --border: #e2e8f0; --shadow: 0 1px 3px rgba(0,0,0,0.06), 0 1px 2px rgba(0,0,0,0.04);
  --shadow-md: 0 4px 16px rgba(0,0,0,0.08); --radius: 14px; --radius-sm: 10px;
  --nav-height: 60px;
}
* { margin: 0; padding: 0; box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Microsoft YaHei", sans-serif;
  background: var(--bg); color: var(--text); line-height: 1.7; -webkit-font-smoothing: antialiased;
}

/* === Nav === */
.navbar {
  position: fixed; top: 0; left: 0; right: 0; z-index: 1000;
  height: var(--nav-height); background: rgba(255,255,255,0.88);
  backdrop-filter: blur(14px); border-bottom: 1px solid var(--border);
  display: flex; align-items: center; justify-content: space-between; padding: 0 32px;
}
.navbar .logo { font-size: 1.2rem; font-weight: 700; color: var(--accent); letter-spacing: 0.5px; text-decoration: none; }
.nav-links { display: flex; gap: 2px; list-style: none; flex-wrap: wrap; justify-content: flex-end; }
.nav-links a {
  color: var(--text-secondary); text-decoration: none;
  font-size: 0.84rem; padding: 6px 14px; border-radius: 20px; transition: all 0.2s; white-space: nowrap;
}
.nav-links a:hover, .nav-links a.active { color: var(--accent); background: var(--accent-bg); }

/* === Hero === */
.hero {
  padding: 120px 32px 80px; text-align: center;
  background: linear-gradient(135deg, rgba(99,102,241,0.04), rgba(129,140,248,0.02));
}
.hero h1 { font-size: 2.8rem; font-weight: 800; color: var(--text); margin-bottom: 12px; letter-spacing: -0.5px; }
.hero h1 span { color: var(--accent); }
.hero p { color: var(--text-secondary); font-size: 1.08rem; max-width: 600px; margin: 0 auto 28px; }
.hero .tags { display: flex; gap: 10px; justify-content: center; flex-wrap: wrap; }
.hero .tags span {
  padding: 5px 16px; border-radius: 20px; font-size: 0.8rem;
  color: var(--accent); border: 1px solid rgba(99,102,241,0.2); background: var(--accent-bg);
}

/* === Section === */
.section { max-width: 1080px; margin: 0 auto; padding: 70px 32px; }
.section-header { text-align: center; margin-bottom: 44px; }
.section-header h2 { font-size: 1.7rem; font-weight: 700; margin-bottom: 8px; }
.section-header p { color: var(--text-muted); font-size: 0.95rem; }

/* === Cards === */
.cards { display: grid; gap: 20px; }
.cards-2 { grid-template-columns: repeat(2, 1fr); }
.cards-3 { grid-template-columns: repeat(3, 1fr); }
.cards-4 { grid-template-columns: repeat(4, 1fr); }
.card {
  background: var(--bg-card); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 26px 24px;
  transition: all 0.25s; text-decoration: none; color: var(--text); display: block;
}
.card:hover { box-shadow: var(--shadow-md); border-color: var(--accent-light); transform: translateY(-3px); }
.card-icon { font-size: 1.6rem; margin-bottom: 14px; width: 44px; height: 44px; display: flex;
  align-items: center; justify-content: center; border-radius: var(--radius-sm);
  background: var(--accent-bg); color: var(--accent);
}
.card h3 { font-size: 1.08rem; margin-bottom: 8px; }
.card p { color: var(--text-secondary); font-size: 0.9rem; line-height: 1.6; }
.card .count { font-size: 0.78rem; color: var(--accent); margin-top: 10px; font-weight: 500; }

/* Compact cards inside detail pages */
.detail-container .card { padding: 20px; }
.detail-container .card p { font-size: 0.85rem; }
.detail-container .cards { margin: 18px 0; }

/* === Footer === */
.footer {
  text-align: center; padding: 36px 24px; border-top: 1px solid var(--border);
  color: var(--text-muted); font-size: 0.84rem; margin-top: 40px;
}

/* === Back link === */
.back-link { display: inline-block; margin-top: 32px; color: var(--accent); text-decoration: none;
  font-size: 0.9rem; padding: 8px 20px; border-radius: 20px; border: 1px solid rgba(99,102,241,0.25); transition: all 0.2s; }
.back-link:hover { background: var(--accent-bg); }

/* === Detail page === */
.detail-page { padding-top: 100px; padding-bottom: 40px; }
.detail-container { max-width: 820px; margin: 0 auto; padding: 0 32px; }
.detail-container h1 { font-size: 2rem; margin-bottom: 8px; }
.detail-container h2 { font-size: 1.3rem; margin: 34px 0 14px; padding-bottom: 8px; border-bottom: 2px solid var(--accent-bg); }
.detail-container h3 { font-size: 1.08rem; margin: 24px 0 10px; }
.detail-container p { color: var(--text-secondary); font-size: 0.95rem; margin-bottom: 12px; }
.detail-container ul, .detail-container ol { color: var(--text-secondary); font-size: 0.95rem; padding-left: 22px; margin-bottom: 14px; }
.detail-container li { margin-bottom: 7px; }
.detail-container strong { color: var(--text); }

/* === Highlight box === */
.highlight {
  background: var(--accent-bg); border-left: 3px solid var(--accent);
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0; padding: 16px 20px; margin: 20px 0;
}
.highlight p { color: var(--text) !important; margin-bottom: 0 !important; }

/* === Page meta & tags === */
.page-meta { color: var(--text-muted); font-size: 0.85rem; margin-bottom: 28px; }
.tag { display: inline-block; padding: 3px 12px; border-radius: 16px; font-size: 0.78rem;
  background: var(--accent-bg); color: var(--accent); margin: 2px 6px 2px 0; }

/* === List page === */
.list-page { padding-top: 100px; padding-bottom: 40px; }
.list-container { max-width: 880px; margin: 0 auto; padding: 0 32px; }
.list-container h1 { font-size: 2rem; margin-bottom: 8px; }
.list-container > p.desc { color: var(--text-secondary); margin-bottom: 32px; }
.list-item {
  display: block; text-decoration: none; color: var(--text);
  background: var(--bg-card); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 22px 24px; margin-bottom: 14px; transition: all 0.2s;
}
.list-item:hover { box-shadow: var(--shadow-md); border-color: var(--accent-light); transform: translateY(-2px); }
.list-item h3 { font-size: 1.05rem; margin-bottom: 6px; }
.list-item h3 .arrow { color: var(--accent); font-weight: 400; }
.list-item p { color: var(--text-secondary); font-size: 0.88rem; }
.list-item .tags { margin-top: 10px; }

/* === Table === */
.info-table { width: 100%; border-collapse: collapse; margin: 16px 0; font-size: 0.9rem; }
.info-table th {
  text-align: left; padding: 12px 16px; border-bottom: 2px solid var(--border);
  color: var(--accent); font-size: 0.84rem; font-weight: 600;
}
.info-table td { padding: 12px 16px; border-bottom: 1px solid var(--border); color: var(--text-secondary); }
.info-table tr:hover td { background: var(--accent-bg); }

/* === Skill bar === */
.skill-bar-wrap { margin-bottom: 18px; }
.skill-bar-wrap .skill-name { display: flex; justify-content: space-between; font-size: 0.9rem; margin-bottom: 6px; }
.skill-bar-wrap .skill-name span:last-child { color: var(--text-muted); font-size: 0.82rem; }
.skill-bar { height: 8px; background: var(--border); border-radius: 4px; overflow: hidden; }
.skill-bar .fill { height: 100%; border-radius: 4px; background: linear-gradient(90deg, var(--accent), var(--accent-light)); }

/* === Timeline === */
.timeline { position: relative; padding-left: 28px; margin: 16px 0; }
.timeline::before { content: ''; position: absolute; left: 9px; top: 4px; bottom: 4px; width: 2px; background: var(--border); }
.timeline-item { position: relative; margin-bottom: 22px; padding-left: 18px; }
.timeline-item::before {
  content: ''; position: absolute; left: -24px; top: 8px; width: 10px; height: 10px;
  border-radius: 50%; background: var(--accent); box-shadow: 0 0 0 3px var(--accent-bg);
}
.timeline-item .step { font-size: 0.78rem; color: var(--accent); font-weight: 600; }
.timeline-item h4 { font-size: 0.95rem; margin: 2px 0 4px; }
.timeline-item p { color: var(--text-secondary); font-size: 0.88rem; margin-bottom: 0; }

/* === Glossary (词条网格) === */
.glossary { display: grid; grid-template-columns: repeat(2, 1fr); gap: 12px; margin: 16px 0; }
.glossary-item {
  background: var(--bg-card); border: 1px solid var(--border);
  border-radius: var(--radius-sm); padding: 16px 20px;
}
.glossary-item strong { color: var(--accent); font-size: 0.9rem; }
.glossary-item p { color: var(--text-secondary); font-size: 0.85rem; margin: 4px 0 0 !important; }

/* === Stat grid === */
.stat-grid { display: flex; justify-content: center; gap: 36px; flex-wrap: wrap; padding: 28px 0; margin: 20px 0;
  border-top: 1px solid var(--border); border-bottom: 1px solid var(--border); }
.stat-item { text-align: center; }
.stat-item .num { font-size: 1.8rem; font-weight: 800; color: var(--accent); }
.stat-item .label { color: var(--text-muted); font-size: 0.82rem; margin-top: 2px; }

/* === Breadcrumb === */
.breadcrumb { font-size: 0.85rem; color: var(--text-muted); margin-bottom: 20px; }
.breadcrumb a { color: var(--accent); text-decoration: none; }
.breadcrumb a:hover { text-decoration: underline; }

/* === Code === */
code {
  font-family: "Cascadia Code", "Fira Code", "JetBrains Mono", Consolas, monospace;
  background: var(--accent-bg); padding: 2px 6px; border-radius: 4px; font-size: 0.88em; color: var(--accent);
}
pre {
  background: #1e293b; color: #e2e8f0; padding: 16px 20px;
  border-radius: var(--radius-sm); overflow-x: auto; font-size: 0.85rem;
  line-height: 1.65; margin: 14px 0; -webkit-overflow-scrolling: touch;
}
pre code { background: none; padding: 0; font-size: inherit; color: inherit; border-radius: 0; }

/* ================================================
   MOBILE — major overhaul for content density
   Target: 30-40 chars/line on 375px, reduce scroll
   ================================================ */
@media (max-width: 768px) {
  body { font-size: 15px; }

  /* Nav — horizontal scroll, compact height */
  .navbar { height: 50px; padding: 0 10px; }
  .navbar .logo { font-size: 1rem; flex-shrink: 0; }
  .nav-links {
    overflow-x: auto; -webkit-overflow-scrolling: touch;
    scrollbar-width: none; flex-wrap: nowrap; gap: 0; margin-left: 6px;
    mask-image: linear-gradient(to left, transparent, black 20px);
  }
  .nav-links::-webkit-scrollbar { display: none; }
  .nav-links a { font-size: 0.73rem; padding: 4px 9px; flex-shrink: 0; }

  /* Hero */
  .hero { padding: 80px 14px 36px; }
  .hero h1 { font-size: 1.7rem; }
  .hero p { font-size: 0.9rem; padding: 0 4px; }
  .hero .tags { gap: 6px; }
  .hero .tags span { padding: 4px 10px; font-size: 0.72rem; }

  /* Section — maximize width */
  .section { padding: 36px 10px; }
  .section-header { margin-bottom: 28px; }
  .section-header h2 { font-size: 1.4rem; }
  .section-header p { font-size: 0.88rem; }

  /* Cards grid — single column, tighter */
  .cards-2, .cards-3, .cards-4 { grid-template-columns: 1fr; gap: 12px; }
  .card { padding: 18px 16px; border-radius: var(--radius-sm); }
  .card-icon { width: 38px; height: 38px; font-size: 1.3rem; margin-bottom: 10px; }
  .card h3 { font-size: 1rem; }
  .card p { font-size: 0.85rem; }
  .detail-container .card { padding: 16px; }
  .detail-container .card p { font-size: 0.83rem; }
  .detail-container .cards { margin: 14px 0; gap: 10px; }

  /* Detail page — wide content, reduced padding */
  .detail-page { padding-top: 72px; padding-bottom: 24px; }
  .detail-container { padding: 0 10px; }
  .detail-container h1 { font-size: 1.45rem; margin-bottom: 4px; }
  .detail-container h2 { font-size: 1.12rem; margin: 22px 0 10px; padding-bottom: 5px; }
  .detail-container h3 { font-size: 0.98rem; margin: 16px 0 8px; }
  .detail-container p { font-size: 0.9rem; margin-bottom: 10px; }
  .detail-container ul, .detail-container ol { font-size: 0.9rem; padding-left: 18px; margin-bottom: 10px; }
  .detail-container li { margin-bottom: 5px; }

  /* Highlight */
  .highlight { padding: 12px 14px; margin: 14px 0; border-radius: 0 8px 8px 0; }
  .highlight p { font-size: 0.9rem !important; }

  /* List page */
  .list-page { padding-top: 72px; padding-bottom: 24px; }
  .list-container { padding: 0 10px; }
  .list-container h1 { font-size: 1.45rem; }
  .list-container > p.desc { font-size: 0.88rem; margin-bottom: 18px; }
  .list-item { padding: 16px; margin-bottom: 10px; border-radius: var(--radius-sm); }
  .list-item h3 { font-size: 0.96rem; }
  .list-item p { font-size: 0.84rem; }
  .list-item .tags { margin-top: 6px; }

  /* Breadcrumb */
  .breadcrumb { font-size: 0.75rem; margin-bottom: 10px; }

  /* Page meta */
  .page-meta { font-size: 0.78rem; margin-bottom: 16px; }
  .tag { padding: 2px 9px; font-size: 0.7rem; }

  /* Table — horizontal scroll on wide tables */
  .info-table { font-size: 0.8rem; }
  .info-table th, .info-table td { padding: 7px 8px; }

  /* Timeline */
  .timeline { padding-left: 22px; }
  .timeline-item { margin-bottom: 16px; padding-left: 14px; }
  .timeline-item::before { left: -20px; width: 8px; height: 8px; }
  .timeline::before { left: 7px; }
  .timeline-item .step { font-size: 0.73rem; }
  .timeline-item h4 { font-size: 0.88rem; }
  .timeline-item p { font-size: 0.83rem; }

  /* Glossary */
  .glossary { grid-template-columns: 1fr; gap: 8px; }
  .glossary-item { padding: 13px 14px; }
  .glossary-item strong { font-size: 0.84rem; }
  .glossary-item p { font-size: 0.8rem; }

  /* Stats */
  .stat-grid { gap: 12px; padding: 16px 0; margin: 14px 0; }
  .stat-item .num { font-size: 1.3rem; }
  .stat-item .label { font-size: 0.72rem; }

  /* Skill bars */
  .skill-bar-wrap { margin-bottom: 14px; }
  .skill-bar-wrap .skill-name { font-size: 0.84rem; }

  /* Code — full width, smaller */
  code { font-size: 0.83em; padding: 1px 5px; }
  pre { padding: 12px 14px; font-size: 0.78rem; border-radius: 8px; margin: 10px 0; }

  /* Footer */
  .footer { padding: 20px 12px; font-size: 0.78rem; margin-top: 20px; }

  /* Back link */
  .back-link { font-size: 0.84rem; padding: 6px 14px; margin-top: 18px; }
}

/* Extra small devices (320-400px) */
@media (max-width: 420px) {
  .detail-container { padding: 0 8px; }
  .list-container { padding: 0 8px; }
  .hero { padding: 76px 8px 30px; }
  .hero h1 { font-size: 1.5rem; }
  .nav-links a { font-size: 0.7rem; padding: 3px 7px; }
  .card { padding: 16px 14px; }
  .list-item { padding: 14px; }
  .list-item h3 { font-size: 0.92rem; }
  .info-table { font-size: 0.75rem; }
  .info-table th, .info-table td { padding: 6px 6px; }
  pre { padding: 10px 12px; font-size: 0.74rem; }
}