:root {
  --bg: #f8f9fa;
  --card: #ffffff;
  --text: #1a1a1a;
  --muted: #6b7280;
  --accent: #2563eb;
  --accent-light: #eff6ff;
  --border: #e5e7eb;
  --heading: #111827;
  --chinese: #b45309;
}

* { margin: 0; padding: 0; box-sizing: border-box; }

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', system-ui, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.7;
  font-size: 15px;
  -webkit-font-smoothing: antialiased;
}

.container { max-width: 960px; margin: 0 auto; padding: 0 20px; }

/* ── Nav ── */
nav {
  background: var(--card);
  border-bottom: 1px solid var(--border);
  padding: 0;
  position: sticky;
  top: 0;
  z-index: 100;
  box-shadow: 0 1px 3px rgba(0,0,0,0.04);
}

.nav-inner {
  display: flex;
  align-items: center;
  min-height: 52px;
  gap: 24px;
}

.logo {
  font-size: 17px;
  font-weight: 700;
  color: var(--heading);
  text-decoration: none;
  letter-spacing: -0.5px;
  white-space: nowrap;
}

.logo span {
  color: var(--muted);
  font-weight: 400;
  font-size: 13px;
  margin-left: 6px;
}

.links {
  display: flex;
  gap: 4px;
  flex-wrap: wrap;
}

.links a {
  color: var(--muted);
  text-decoration: none;
  font-size: 13px;
  padding: 6px 10px;
  border-radius: 6px;
  transition: all 0.15s;
  white-space: nowrap;
}

.links a:hover, .links a.active {
  color: var(--accent);
  background: var(--accent-light);
}

.hamburger {
  display: none;
  background: none;
  border: none;
  cursor: pointer;
  padding: 8px;
  margin-left: auto;
  flex-direction: column;
  gap: 4px;
}

.hamburger span {
  display: block;
  width: 20px;
  height: 2px;
  background: var(--heading);
  border-radius: 1px;
  transition: all 0.2s;
}

/* ── Main ── */
main { padding: 32px 0 80px; }

/* ── Home ── */
.hero {
  text-align: center;
  padding: 48px 0 32px;
}

.hero h1 {
  font-size: 28px;
  font-weight: 700;
  color: var(--heading);
  margin-bottom: 6px;
}

.hero .subtitle {
  color: var(--muted);
  font-size: 15px;
}

.cards {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
  margin-top: 32px;
}

.card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 24px;
  text-decoration: none;
  color: var(--text);
  transition: all 0.2s;
}

.card:hover {
  border-color: var(--accent);
  box-shadow: 0 4px 12px rgba(37,99,235,0.08);
  transform: translateY(-1px);
}

.card h3 { font-size: 17px; color: var(--heading); margin-bottom: 2px; }
.card .zh { color: var(--chinese); font-size: 15px; margin-bottom: 8px; }
.card p { color: var(--muted); font-size: 13px; line-height: 1.5; }

.badge {
  display: inline-block;
  font-size: 11px;
  padding: 2px 8px;
  border-radius: 4px;
  margin-top: 12px;
  font-weight: 600;
}

.badge.checklist { background: #ecfdf5; color: #059669; }
.badge.reference { background: #fef3c7; color: #92400e; }

/* ── Content pages ── */
.content {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 36px 44px;
}

.content h1 {
  font-size: 24px;
  font-weight: 700;
  color: var(--heading);
  margin-bottom: 8px;
  padding-bottom: 14px;
  border-bottom: 2px solid var(--accent);
}

.content h2 {
  font-size: 20px;
  font-weight: 700;
  color: var(--heading);
  margin-top: 40px;
  margin-bottom: 12px;
  padding: 10px 14px;
  background: #f0f4ff;
  border-left: 4px solid var(--accent);
  border-radius: 0 6px 6px 0;
}

.content h2:first-of-type { margin-top: 20px; }

.content h3 {
  font-size: 16px;
  font-weight: 600;
  color: var(--heading);
  margin-top: 24px;
  margin-bottom: 6px;
  padding-bottom: 4px;
  border-bottom: 1px solid var(--border);
}

.content h4 {
  font-size: 13.5px;
  font-weight: 600;
  color: var(--muted);
  margin-top: 16px;
  margin-bottom: 4px;
  padding-left: 12px;
  border-left: 2px solid var(--border);
}

.content p { margin-bottom: 6px; }

.content ul { list-style: none; padding-left: 0; }

.content li {
  padding: 2px 0 2px 18px;
  position: relative;
  line-height: 1.65;
}

.content li::before {
  content: '•';
  position: absolute;
  left: 3px;
  color: var(--muted);
}

.content li li { padding-left: 18px; }
.content li li::before { content: '◦'; }
.content li li li { padding-left: 18px; }
.content li li li::before { content: '▪'; font-size: 10px; }
.content li li li li::before { content: '–'; }

.content blockquote {
  background: var(--accent-light);
  border-left: 3px solid var(--accent);
  padding: 10px 14px;
  margin: 10px 0;
  border-radius: 0 8px 8px 0;
  font-size: 13.5px;
  color: #374151;
}

.content blockquote p { margin: 0; }
.content strong { font-weight: 600; color: var(--heading); }

.content hr {
  border: none;
  border-top: 2px solid var(--border);
  margin: 28px 0;
}

/* ── Mobile ── */
@media (max-width: 768px) {
  .hamburger { display: flex; }

  .nav-inner .links {
    display: none;
    position: absolute;
    top: 52px;
    left: 0;
    right: 0;
    background: var(--card);
    border-bottom: 1px solid var(--border);
    flex-direction: column;
    padding: 8px 16px 12px;
    box-shadow: 0 4px 12px rgba(0,0,0,0.06);
  }

  .nav-inner.open .links { display: flex; }

  .nav-inner .links a {
    padding: 10px 12px;
    font-size: 14px;
    border-radius: 8px;
  }

  .cards { grid-template-columns: 1fr; }

  .content { padding: 20px 16px; border-radius: 8px; }
  .content h1 { font-size: 20px; }
  .content h2 { font-size: 17px; }

  .hero { padding: 32px 0 20px; }
  .hero h1 { font-size: 24px; }

  main { padding: 20px 0 60px; }
}

@media (max-width: 480px) {
  .logo span { display: none; }
  .content { padding: 16px 14px; }
  .content li { font-size: 14px; }
}

/* ── Print ── */
@media print {
  nav { display: none; }
  .content { border: none; padding: 0; box-shadow: none; }
  body { font-size: 11px; }
}