:root {
  --bg: #0f172a;
  --panel: #111c33;
  --card: #17233d;
  --text: #e5edf8;
  --muted: #9fb0c7;
  --accent: #7dd3fc;
  --accent-2: #a78bfa;
  --line: rgba(255,255,255,.12);
  --shadow: 0 24px 80px rgba(0,0,0,.28);
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  font-family: "Segoe UI", "Microsoft YaHei", system-ui, sans-serif;
  background: radial-gradient(circle at top left, #1e3a8a 0, transparent 36%), var(--bg);
  color: var(--text);
  line-height: 1.7;
}
a { color: inherit; text-decoration: none; }
code { background: rgba(255,255,255,.08); padding: .12rem .35rem; border-radius: .35rem; }
.hero { min-height: 74vh; padding: 24px clamp(20px, 5vw, 72px); }
.topbar { display: flex; align-items: center; justify-content: space-between; gap: 24px; }
.brand { font-weight: 800; letter-spacing: .04em; }
.navlinks { display: flex; gap: 18px; color: var(--muted); font-size: 14px; }
.navlinks a:hover { color: var(--accent); }
.hero-content { max-width: 920px; padding: 110px 0 48px; }
.eyebrow { color: var(--accent); font-weight: 800; text-transform: uppercase; letter-spacing: .14em; font-size: 13px; }
h1 { font-size: clamp(42px, 7vw, 76px); line-height: 1.05; margin: 10px 0 22px; }
h2 { font-size: clamp(28px, 4vw, 44px); margin: 0; }
h3 { margin: 0 0 10px; }
.subtitle { max-width: 760px; color: var(--muted); font-size: 20px; }
.hero-actions { display: flex; gap: 14px; flex-wrap: wrap; margin-top: 34px; }
.button { border: 1px solid var(--line); border-radius: 999px; padding: 12px 20px; font-weight: 700; }
.button.primary { background: linear-gradient(135deg, var(--accent), var(--accent-2)); color: #08111f; border: 0; }
.button.ghost { color: var(--text); background: rgba(255,255,255,.06); }
main { padding: 0 clamp(20px, 5vw, 72px) 64px; }
.panel { max-width: 1180px; margin: 0 auto 28px; padding: clamp(22px, 4vw, 42px); background: rgba(17,28,51,.76); border: 1px solid var(--line); border-radius: 28px; box-shadow: var(--shadow); backdrop-filter: blur(10px); }
.section-title { display: flex; justify-content: space-between; gap: 24px; align-items: end; margin-bottom: 24px; }
.grid { display: grid; gap: 16px; }
.cards { grid-template-columns: repeat(4, minmax(0, 1fr)); }
.cards article, .term, .timeline-item, .lesson-card, .lesson-list, .progress-box { background: var(--card); border: 1px solid var(--line); border-radius: 20px; padding: 20px; }
.cards p, .term p, .timeline-item p, .progress-box p { color: var(--muted); margin-bottom: 0; }
.timeline { display: grid; gap: 14px; }
.timeline-item { display: grid; grid-template-columns: 110px 1fr; gap: 18px; }
.phase { color: var(--accent); font-weight: 900; }
.lesson-layout { display: grid; grid-template-columns: 300px 1fr; gap: 18px; align-items: start; }
.lesson-list { display: grid; gap: 10px; position: sticky; top: 18px; }
.lesson-button { width: 100%; text-align: left; padding: 12px 14px; border: 1px solid var(--line); border-radius: 14px; background: rgba(255,255,255,.04); color: var(--text); cursor: pointer; }
.lesson-button.active { background: rgba(125,211,252,.16); border-color: rgba(125,211,252,.55); }
.lesson-card h3 { font-size: 28px; }
.lesson-card .tag { display: inline-block; margin: 0 8px 8px 0; padding: 4px 9px; border-radius: 999px; background: rgba(167,139,250,.18); color: #ddd6fe; font-size: 13px; }
.lesson-card li { margin: 8px 0; }
.glossary { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 16px; }
.handoff-list li { margin: 10px 0; }
footer { color: var(--muted); text-align: center; padding: 28px; }
@media (max-width: 860px) {
  .topbar, .section-title { align-items: flex-start; flex-direction: column; }
  .cards, .glossary, .lesson-layout { grid-template-columns: 1fr; }
  .timeline-item { grid-template-columns: 1fr; }
  .lesson-list { position: static; }
}