:root {
  --c-bg: #FFFFFF;
  --c-bg-soft: #F8FAFC;
  --c-bg-card: #F1F5F9;
  --c-primary: #2563EB;
  --c-primary-dark: #1E40AF;
  --c-primary-light: #DBEAFE;
  --c-accent: #7C3AED;
  --c-accent-light: #EDE9FE;
  --c-text: #1E293B;
  --c-text-soft: #64748B;
  --c-text-light: #94A3B8;
  --c-border: #E2E8F0;
  --c-success: #059669;
  --c-danger: #DC2626;
  --c-warn: #D97706;
  --radius-sm: 8px;
  --radius-md: 14px;
  --radius-lg: 22px;
  --shadow-sm: 0 1px 3px rgba(0,0,0,0.08);
  --shadow-md: 0 4px 12px rgba(0,0,0,0.08);
  --shadow-lg: 0 8px 30px rgba(0,0,0,0.10);
  --max-w: 1080px;
  --font-stack: -apple-system, "PingFang SC", "Microsoft YaHei", "Noto Sans CJK SC", sans-serif;
}

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

html { scroll-behavior: smooth; }

body {
  font-family: var(--font-stack);
  background: var(--c-bg);
  color: var(--c-text);
  line-height: 1.8;
  font-size: 16px;
  overflow-x: hidden;
}

/* === Top Nav === */
.top-nav {
  position: fixed; top: 0; left: 0; right: 0;
  height: 64px;
  background: rgba(255,255,255,0.92);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--c-border);
  z-index: 1000;
  display: flex; align-items: center; justify-content: space-between;
  padding: 0 24px;
}
.top-nav .logo {
  font-size: 18px; font-weight: 700; color: var(--c-primary);
  white-space: nowrap;
}
.top-nav .nav-links {
  display: flex; gap: 4px; list-style: none;
}
.top-nav .nav-links a {
  text-decoration: none; color: var(--c-text-soft);
  font-size: 14px; padding: 8px 14px; border-radius: var(--radius-sm);
  transition: all 0.2s;
}
.top-nav .nav-links a:hover, .top-nav .nav-links a.active {
  color: var(--c-primary); background: var(--c-primary-light);
}
.top-nav .print-btns {
  display: flex; gap: 8px;
}
.top-nav .print-btn {
  padding: 7px 14px; border-radius: var(--radius-sm);
  font-size: 13px; border: none; cursor: pointer;
  font-family: var(--font-stack); font-weight: 600;
  transition: all 0.2s;
}
.print-btn.adult { background: var(--c-primary); color: #fff; }
.print-btn.child { background: var(--c-accent-light); color: var(--c-accent); }
.print-btn:hover { transform: translateY(-1px); box-shadow: var(--shadow-sm); }

.nav-toggle { display: none; }

/* === Hero === */
.hero {
  margin-top: 64px;
  padding: 60px 24px 48px;
  text-align: center;
  background: linear-gradient(135deg, #EFF6FF 0%, #F5F3FF 50%, #ECFEFF 100%);
}
.hero h1 {
  font-size: 36px; font-weight: 800;
  background: linear-gradient(135deg, #2563EB, #7C3AED);
  -webkit-background-clip: text; -webkit-text-fill-color: transparent;
  background-clip: text;
  margin-bottom: 16px;
}
.hero .subtitle {
  font-size: 18px; color: var(--c-text-soft); max-width: 720px; margin: 0 auto 24px;
}
.hero .meta {
  display: flex; justify-content: center; gap: 20px; flex-wrap: wrap;
  font-size: 13px; color: var(--c-text-light);
}
.hero .meta span { padding: 4px 12px; background: rgba(255,255,255,0.6); border-radius: 20px; }

/* === Chapter Navigation Cards === */
.chapter-nav {
  max-width: var(--max-w);
  margin: 0 auto;
  padding: 40px 24px;
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: 20px;
}
.ch-card {
  background: var(--c-bg-soft);
  border: 1px solid var(--c-border);
  border-radius: var(--radius-md);
  padding: 24px;
  cursor: pointer;
  transition: all 0.3s;
  display: flex; flex-direction: column;
}
.ch-card:hover {
  box-shadow: var(--shadow-md);
  border-color: var(--c-primary);
  transform: translateY(-2px);
}
.ch-card .ch-num {
  display: inline-flex; align-items: center; justify-content: center;
  width: 36px; height: 36px; border-radius: 50%;
  background: var(--c-primary); color: #fff;
  font-size: 16px; font-weight: 700; margin-bottom: 12px;
}
.ch-card h3 { font-size: 18px; margin-bottom: 8px; }
.ch-card p { font-size: 14px; color: var(--c-text-soft); flex: 1; }
.ch-card .ch-go {
  margin-top: 12px; color: var(--c-primary); font-size: 13px; font-weight: 600;
}

/* === Chapter Content === */
.chapter {
  max-width: var(--max-w);
  margin: 0 auto;
  padding: 48px 24px;
  display: none;
}
.chapter.active {
  display: block;
  animation: fadeInUp 0.4s ease;
}
@keyframes fadeInUp {
  from { opacity: 0; transform: translateY(20px); }
  to { opacity: 1; transform: translateY(0); }
}
.chapter.leaving { animation: fadeOutDown 0.3s ease forwards; }
@keyframes fadeOutDown {
  from { opacity: 1; transform: translateY(0); }
  to { opacity: 0; transform: translateY(-20px); }
}

.chapter-header {
  margin-bottom: 32px;
  padding-bottom: 20px;
  border-bottom: 2px solid var(--c-primary-light);
}
.chapter-header .ch-label {
  font-size: 13px; color: var(--c-primary); font-weight: 600;
  text-transform: uppercase; letter-spacing: 1px;
}
.chapter-header h2 {
  font-size: 28px; margin: 8px 0 12px;
}
.chapter-header .ch-summary {
  font-size: 15px; color: var(--c-text-soft);
}

/* === Content Sections === */
.section { margin-bottom: 40px; }
.section h3 {
  font-size: 22px; margin: 24px 0 16px;
  padding-left: 12px; border-left: 4px solid var(--c-primary);
}
.section h4 {
  font-size: 18px; margin: 20px 0 12px; color: var(--c-text);
}
.section p {
  margin-bottom: 16px; font-size: 16px;
}
.section ul, .section ol {
  margin: 12px 0 20px 24px;
}
.section li { margin-bottom: 8px; }

/* === Callout === */
.callout {
  background: var(--c-primary-light);
  border-left: 4px solid var(--c-primary);
  border-radius: var(--radius-sm);
  padding: 16px 20px;
  margin: 20px 0;
}
.callout.warning {
  background: #FEF3C7;
  border-left-color: var(--c-warn);
}
.callout.danger {
  background: #FEE2E2;
  border-left-color: var(--c-danger);
}
.callout.success {
  background: #D1FAE5;
  border-left-color: var(--c-success);
}
.callout p { margin: 0; font-size: 15px; }
.callout strong { color: var(--c-primary); }
.callout.warning strong { color: var(--c-warn); }
.callout.danger strong { color: var(--c-danger); }
.callout.success strong { color: var(--c-success); }

/* === Table === */
.data-table {
  width: 100%; border-collapse: collapse;
  margin: 20px 0; font-size: 14px;
  border-radius: var(--radius-md); overflow: hidden;
  box-shadow: var(--shadow-sm);
}
.data-table th {
  background: var(--c-text); color: #fff;
  padding: 12px 16px; text-align: left; font-weight: 600;
}
.data-table td {
  padding: 12px 16px;
  border-bottom: 1px solid var(--c-border);
}
.data-table tr:nth-child(even) { background: var(--c-bg-soft); }
.data-table tr:hover { background: var(--c-primary-light); }

/* === Image Card === */
.img-card {
  margin: 28px 0;
  text-align: center;
}
.img-card img {
  max-width: 100%; height: auto;
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-md);
}
.img-card .img-caption {
  margin-top: 10px;
  font-size: 13px; color: var(--c-text-light);
}
.img-card .img-caption strong { color: var(--c-text-soft); }

/* === Chapter Footer Nav === */
.chapter-footer {
  margin-top: 48px;
  padding-top: 24px;
  border-top: 1px solid var(--c-border);
  display: flex; justify-content: space-between; align-items: center;
}
.chapter-footer .prev, .chapter-footer .next {
  padding: 10px 20px;
  border-radius: var(--radius-sm);
  font-size: 14px; font-weight: 600;
  cursor: pointer; transition: all 0.2s;
  text-decoration: none; display: inline-flex; align-items: center; gap: 8px;
}
.chapter-footer .prev { color: var(--c-text-soft); border: 1px solid var(--c-border); }
.chapter-footer .next { background: var(--c-primary); color: #fff; }
.chapter-footer .prev:hover { border-color: var(--c-primary); color: var(--c-primary); }
.chapter-footer .next:hover { background: var(--c-primary-dark); }
.chapter-footer .disabled {
  opacity: 0.4; pointer-events: none;
}

/* === Sources === */
.sources-section {
  max-width: var(--max-w);
  margin: 0 auto;
  padding: 48px 24px 80px;
  border-top: 1px solid var(--c-border);
}
.sources-section h3 {
  font-size: 20px; margin-bottom: 16px;
}
.sources-section ol {
  margin-left: 20px;
}
.sources-section li {
  margin-bottom: 10px; font-size: 13px; color: var(--c-text-soft);
}
.sources-section a { color: var(--c-primary); text-decoration: none; }
.sources-section a:hover { text-decoration: underline; }
.verify-date {
  margin-top: 20px; padding: 12px 16px;
  background: var(--c-bg-soft); border-radius: var(--radius-sm);
  font-size: 13px; color: var(--c-text-soft);
}

/* === Mobile === */
@media (max-width: 768px) {
  .top-nav { padding: 0 12px; }
  .top-nav .logo { font-size: 15px; }
  .top-nav .nav-links { display: none; }
  .top-nav .nav-links.open {
    display: flex; flex-direction: column;
    position: absolute; top: 64px; left: 0; right: 0;
    background: #fff; border-bottom: 1px solid var(--c-border);
    padding: 12px; gap: 0;
  }
  .nav-toggle {
    display: flex; flex-direction: column; gap: 4px;
    cursor: pointer; padding: 8px;
  }
  .nav-toggle span { width: 20px; height: 2px; background: var(--c-text); border-radius: 2px; }
  .top-nav .print-btns { gap: 6px; }
  .top-nav .print-btn { font-size: 11px; padding: 6px 10px; }
  .hero { padding: 40px 16px 32px; }
  .hero h1 { font-size: 26px; }
  .hero .subtitle { font-size: 15px; }
  .chapter-nav { grid-template-columns: 1fr; padding: 24px 16px; }
  .chapter { padding: 32px 16px; }
  .chapter-header h2 { font-size: 22px; }
  .section h3 { font-size: 18px; }
  .section p { font-size: 15px; }
  .data-table { font-size: 12px; }
  .data-table th, .data-table td { padding: 8px 10px; }
  .chapter-footer { flex-direction: column; gap: 12px; }
}

/* === Print === */
@media print {
  body { font-size: 12pt; line-height: 1.6; color: #000; }
  .top-nav, .chapter-nav, .chapter-footer, .nav-toggle { display: none !important; }
  .chapter { display: block !important; page-break-after: always; }
  .chapter-header { page-break-after: avoid; }
  .section h3, .section h4 { page-break-after: avoid; }
  .img-card { page-break-inside: avoid; }
  .img-card img { max-width: 100%; box-shadow: none; }
  .callout { page-break-inside: avoid; }
  .data-table { page-break-inside: avoid; }
  .sources-section { page-break-before: always; }
}

body.print-adult .chapter { display: block !important; }
body.print-adult .chapter-nav { display: none !important; }
body.print-adult .top-nav { display: none !important; }

body.print-child .chapter { display: none !important; }
body.print-child .chapter-header .ch-summary { display: none; }
body.print-child .section p, body.print-child .section ul, body.print-child .section ol,
body.print-child .callout, body.print-child .data-table { display: none !important; }
body.print-child .chapter { display: block !important; }
body.print-child .img-card { display: block !important; page-break-inside: avoid; }
body.print-child .img-card .img-caption { display: block; }
body.print-child .chapter-header { display: block; }
body.print-child .section h3 { display: block; page-break-after: avoid; }
body.print-child .sources-section { display: none !important; }

@media (prefers-reduced-motion: reduce) {
  .chapter.active { animation: none; }
  .chapter.leaving { animation: none; }
  html { scroll-behavior: auto; }
  * { transition: none !important; }
}