:root {
  --bg: #f7f6f2;
  --surface: #ffffff;
  --surface-2: #f0eee8;
  --text: #1f1e1b;
  --muted: #6b6860;
  --border: #e3e0d8;
  --accent: #3b5bdb;
  --good: #2b8a3e;
  --bad: #c92a2a;
  --shadow: 0 1px 2px rgba(0,0,0,.04), 0 4px 16px rgba(0,0,0,.05);
  --radius: 14px;
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #15161a; --surface: #1e2026; --surface-2: #262830; --text: #ecebe6;
    --muted: #9c9a92; --border: #30323a; --accent: #7c93f5; --good: #51cf66; --bad: #ff6b6b;
    --shadow: 0 1px 2px rgba(0,0,0,.3), 0 4px 16px rgba(0,0,0,.25);
  }
}
:root[data-theme="dark"] {
  --bg: #15161a; --surface: #1e2026; --surface-2: #262830; --text: #ecebe6;
  --muted: #9c9a92; --border: #30323a; --accent: #7c93f5; --good: #51cf66; --bad: #ff6b6b;
  --shadow: 0 1px 2px rgba(0,0,0,.3), 0 4px 16px rgba(0,0,0,.25);
}

* { box-sizing: border-box; }
html, body { margin: 0; }
body {
  background: var(--bg); color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  line-height: 1.7; min-height: 100vh; display: flex; flex-direction: column;
}
a { color: inherit; text-decoration: none; }
button { font: inherit; color: inherit; }

/* Top bar */
.topbar {
  position: sticky; top: 0; z-index: 10;
  display: flex; align-items: center; gap: 16px;
  padding: 12px 24px; background: color-mix(in srgb, var(--bg) 88%, transparent);
  backdrop-filter: blur(10px); border-bottom: 1px solid var(--border);
}
.brand { font-weight: 700; font-size: 20px; display: flex; align-items: center; gap: 8px; white-space: nowrap; }
.brand-mark {
  display: inline-grid; place-items: center; width: 32px; height: 32px; border-radius: 9px;
  background: var(--accent); color: #fff; font-size: 18px;
}
.search-wrap { position: relative; flex: 1; max-width: 460px; margin-left: auto; }
#search {
  width: 100%; padding: 9px 14px; border-radius: 10px; border: 1px solid var(--border);
  background: var(--surface); color: var(--text); font-size: 14px; outline: none;
}
#search:focus { border-color: var(--accent); }
.search-results {
  position: absolute; top: calc(100% + 6px); left: 0; right: 0; background: var(--surface);
  border: 1px solid var(--border); border-radius: 12px; box-shadow: var(--shadow);
  max-height: 60vh; overflow: auto; padding: 6px;
}
.search-results a { display: block; padding: 8px 10px; border-radius: 8px; }
.search-results a:hover, .search-results a.active { background: var(--surface-2); }
.search-results small { color: var(--muted); margin-left: 6px; }
.search-empty { padding: 10px; color: var(--muted); font-size: 14px; }
.icon-btn {
  border: 1px solid var(--border); background: var(--surface); border-radius: 10px;
  width: 38px; height: 38px; cursor: pointer; font-size: 18px;
}

main { flex: 1; width: 100%; max-width: 1080px; margin: 0 auto; padding: 32px 24px 64px; }
.footer { text-align: center; color: var(--muted); font-size: 13px; padding: 24px; border-top: 1px solid var(--border); }

/* Breadcrumb */
.crumbs { font-size: 14px; color: var(--muted); margin-bottom: 18px; }
.crumbs a:hover { color: var(--accent); }
.crumbs span.sep { margin: 0 6px; }

/* Hero */
.hero { margin-bottom: 36px; }
.hero h1 { font-size: 36px; line-height: 1.25; margin: 0 0 10px; letter-spacing: -.5px; }
.hero p { color: var(--muted); margin: 0; font-size: 17px; max-width: 640px; }
.stats { display: flex; gap: 12px; margin-top: 20px; flex-wrap: wrap; }
.stat { background: var(--surface); border: 1px solid var(--border); border-radius: 12px; padding: 10px 16px; }
.stat b { font-size: 20px; display: block; line-height: 1.2; }
.stat span { font-size: 13px; color: var(--muted); }

/* Domain grid */
.grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(300px, 1fr)); gap: 18px; }
.card {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 22px; box-shadow: var(--shadow); transition: transform .15s, border-color .15s;
  display: block; position: relative; overflow: hidden;
}
.card:hover { transform: translateY(-2px); border-color: var(--c, var(--accent)); }
.domain-card::before {
  content: ""; position: absolute; inset: 0 0 auto 0; height: 4px; background: var(--c);
}
.domain-icon {
  width: 48px; height: 48px; border-radius: 12px; display: grid; place-items: center; font-size: 24px;
  background: color-mix(in srgb, var(--c) 14%, transparent); margin-bottom: 14px;
}
.card h3 { margin: 0 0 6px; font-size: 20px; }
.card p { margin: 0; color: var(--muted); font-size: 14px; }
.progress { height: 6px; background: var(--surface-2); border-radius: 99px; margin-top: 16px; overflow: hidden; }
.progress > div { height: 100%; background: var(--c, var(--accent)); border-radius: 99px; transition: width .3s; }
.progress-label { font-size: 12px; color: var(--muted); margin-top: 6px; }

/* Domain page */
.domain-head { display: flex; gap: 18px; align-items: center; margin-bottom: 30px; }
.domain-head .domain-icon { width: 64px; height: 64px; font-size: 32px; margin: 0; }
.domain-head h1 { margin: 0; font-size: 30px; }
.domain-head p { margin: 2px 0 0; color: var(--muted); }
.cat-tabs { display: flex; gap: 8px; flex-wrap: wrap; margin-bottom: 20px; }
.cat-tab {
  padding: 6px 14px; border-radius: 99px; border: 1px solid var(--border); background: var(--surface);
  cursor: pointer; font-size: 14px;
}
.cat-tab.on { background: var(--c); border-color: var(--c); color: #fff; }
.category { margin-bottom: 36px; }
.category h2 { font-size: 20px; margin: 0 0 4px; display: flex; align-items: center; gap: 8px; }
.category h2::before { content: ""; width: 4px; height: 18px; border-radius: 2px; background: var(--c); }
.category > p { color: var(--muted); margin: 0 0 14px; font-size: 14px; }
.topic-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(240px, 1fr)); gap: 14px; }
.topic-card { padding: 18px; }
.topic-card h3 { font-size: 17px; }
.topic-card .formula-mini { margin: 10px 0 0; color: var(--text); font-size: 13px; overflow-x: auto; overflow-y: hidden; }
.badges { display: flex; gap: 6px; margin-top: 12px; flex-wrap: wrap; }
.badge { font-size: 11px; padding: 2px 8px; border-radius: 99px; background: var(--surface-2); color: var(--muted); }
.badge.done { background: color-mix(in srgb, var(--good) 16%, transparent); color: var(--good); }
.badge.demo { background: color-mix(in srgb, var(--c) 16%, transparent); color: var(--c); }

/* Topic page */
.topic { max-width: 780px; margin: 0 auto; }
.topic-title { font-size: 34px; margin: 0; line-height: 1.3; }
.topic-sub { color: var(--muted); margin: 6px 0 24px; font-size: 17px; }
.formula-box {
  background: var(--surface); border: 1px solid var(--border); border-left: 4px solid var(--c);
  border-radius: var(--radius); padding: 22px; font-size: 20px; overflow-x: auto; margin-bottom: 8px;
}
.formula-note { color: var(--muted); font-size: 14px; margin-bottom: 28px; }
.section { margin: 32px 0; }
.section h2 { font-size: 21px; margin: 0 0 12px; display: flex; align-items: center; gap: 8px; }
.section p { margin: 0 0 12px; }
.life-list { display: grid; gap: 12px; }
.life-item {
  background: var(--surface); border: 1px solid var(--border); border-radius: 12px; padding: 14px 18px;
}
.life-item b { display: block; margin-bottom: 2px; }
.life-item span { color: var(--muted); font-size: 15px; }
.example {
  background: color-mix(in srgb, var(--c) 7%, var(--surface)); border-radius: 12px; padding: 16px 20px;
  border: 1px dashed color-mix(in srgb, var(--c) 40%, transparent);
}

/* Demo */
.demo {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 20px; box-shadow: var(--shadow);
}
.demo-controls { display: grid; grid-template-columns: repeat(auto-fit, minmax(200px, 1fr)); gap: 12px 20px; margin-bottom: 16px; }
.demo label { font-size: 14px; color: var(--muted); display: block; }
.demo label output { color: var(--text); font-weight: 600; float: right; }
.demo input[type=range] { width: 100%; accent-color: var(--c); }
.demo canvas { width: 100%; height: 280px; display: block; border-radius: 10px; background: var(--surface-2); }
.demo-out { margin-top: 14px; font-size: 15px; }
.demo-out b { color: var(--c); }
.demo-metrics { display: grid; grid-template-columns: repeat(auto-fit, minmax(155px, 1fr)); gap: 10px; margin: 4px 0 12px; }
.demo-metric { border: 1px solid var(--border); background: var(--surface-2); border-radius: 10px; padding: 12px 14px; min-width: 0; }
.demo-metric span { color: var(--muted); font-size: 13px; display: block; }
.demo-metric b { color: var(--c); font-size: 18px; overflow-wrap: anywhere; }
.demo-hint { color: var(--muted); font-size: 14px; margin: 10px 0 0; }
.interval-track { height: 20px; border-radius: 99px; background: var(--surface-2); position: relative; margin: 18px 3px; }
.interval-track span { position: absolute; top: 3px; height: 14px; border-radius: 99px; background: color-mix(in srgb, var(--c) 35%, var(--surface)); }
.interval-track i { position: absolute; top: 0; height: 20px; width: 3px; background: var(--c); }
.demo-steps { display: flex; gap: 6px; flex-wrap: wrap; color: var(--muted); margin: 10px 0; }
.demo-steps span { padding: 4px 9px; border-radius: 8px; border: 1px solid var(--border); color: var(--text); }
.route-grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 10px; }
.route-card { border: 1px solid var(--border); background: var(--surface-2); border-radius: 10px; padding: 14px; }
.route-card.best { border-color: var(--c); background: color-mix(in srgb, var(--c) 9%, var(--surface)); }
.route-card b, .route-card small { display: block; }
.route-card b { color: var(--c); font-size: 20px; }
.route-card small { color: var(--muted); }
.btn {
  padding: 8px 16px; border-radius: 10px; border: 1px solid var(--border); background: var(--surface-2);
  cursor: pointer; font-size: 14px;
}
.btn:hover { border-color: var(--c); }
.btn.primary { background: var(--c); color: #fff; border-color: var(--c); }
.btn-row { display: flex; gap: 8px; flex-wrap: wrap; margin-bottom: 12px; }
.doors { display: flex; gap: 14px; justify-content: center; margin: 16px 0; }
.door {
  width: 90px; height: 130px; border-radius: 10px 10px 4px 4px; border: 2px solid var(--border);
  background: color-mix(in srgb, var(--c) 18%, var(--surface)); cursor: pointer; font-size: 34px;
  display: grid; place-items: center; transition: transform .15s;
}
.door:hover { transform: translateY(-3px); }
.door.picked { border-color: var(--c); box-shadow: 0 0 0 3px color-mix(in srgb, var(--c) 30%, transparent); }
.door.open { background: var(--surface-2); cursor: default; }
.table { width: 100%; border-collapse: collapse; font-size: 14px; }
.table th, .table td { padding: 8px 10px; border-bottom: 1px solid var(--border); text-align: left; }
.table th { color: var(--muted); font-weight: 500; }
.matrix { border-collapse: collapse; margin: 8px auto; font-size: 14px; }
.matrix td, .matrix th { border: 1px solid var(--border); padding: 10px 14px; text-align: center; }
.matrix th { background: var(--surface-2); font-weight: 500; }

/* Quiz */
.quiz { background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius); padding: 20px; }
.quiz-q { font-weight: 600; margin-bottom: 12px; }
.quiz-opt {
  display: block; width: 100%; text-align: left; padding: 10px 14px; margin-bottom: 8px; border-radius: 10px;
  border: 1px solid var(--border); background: var(--surface); cursor: pointer;
}
.quiz-opt:hover:not(:disabled) { border-color: var(--c); }
.quiz-opt.right { border-color: var(--good); background: color-mix(in srgb, var(--good) 12%, transparent); }
.quiz-opt.wrong { border-color: var(--bad); background: color-mix(in srgb, var(--bad) 12%, transparent); }
.quiz-why { margin-top: 10px; color: var(--muted); font-size: 15px; }

.topic-foot { display: flex; justify-content: space-between; gap: 12px; margin-top: 40px; flex-wrap: wrap; align-items: center; }
.mark-btn.done { background: var(--good); border-color: var(--good); color: #fff; }
.nav-links { display: flex; gap: 10px; flex-wrap: wrap; }

@media (max-width: 640px) {
  .topbar { padding: 10px 16px; gap: 10px; }
  .brand { font-size: 17px; }
  main { padding: 20px 16px 48px; }
  .hero h1 { font-size: 27px; }
  .topic-title { font-size: 26px; }
  .formula-box { font-size: 16px; padding: 16px; }
  .grid { grid-template-columns: 1fr; }
  .door { width: 70px; height: 104px; }
}