:root {
  --bg: #f6f8fb;
  --surface: #ffffff;
  --text: #1f2937;
  --muted: #5b6470;
  --primary: #234a78;
  --primary-light: #dce8f7;
  --border: #d7dee7;
  --code-bg: #111827;
  --code-text: #e5edf8;
  --accent: #f2c66d;
  --shadow: 0 8px 24px rgba(0, 0, 0, 0.06);
  --radius: 14px;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  font-family: "Microsoft JhengHei", "Noto Sans TC", sans-serif;
  line-height: 1.8;
  color: var(--text);
  background: var(--bg);
}

a {
  color: var(--primary);
  text-decoration: none;
}

a:hover {
  text-decoration: underline;
}

.container {
  width: min(1100px, 92%);
  margin: 0 auto;
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 20;
  background: rgba(255, 255, 255, 0.96);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--border);
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  min-height: 64px;
  gap: 16px;
}

.brand {
  font-weight: 700;
  color: var(--primary);
}

.top-nav {
  display: flex;
  gap: 16px;
}

.top-nav a {
  padding: 8px 10px;
  border-radius: 8px;
}

.top-nav a.active,
.top-nav a:hover {
  background: var(--primary-light);
  text-decoration: none;
}

.menu-toggle {
  display: none;
  border: 1px solid var(--border);
  background: var(--surface);
  padding: 8px 12px;
  border-radius: 10px;
  cursor: pointer;
}

.hero {
  background: linear-gradient(135deg, #18385d 0%, #315b8d 100%);
  color: #fff;
  padding: 72px 0;
}

.eyebrow {
  display: inline-block;
  margin: 0 0 8px;
  padding: 4px 10px;
  background: rgba(255,255,255,0.14);
  border-radius: 999px;
  font-size: 0.95rem;
}

.hero h1 {
  margin: 0 0 14px;
  font-size: clamp(2rem, 4vw, 3.2rem);
  line-height: 1.25;
}

.hero-text {
  max-width: 780px;
  color: rgba(255,255,255,0.9);
}

.hero-actions {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
  margin-top: 20px;
}

.btn {
  display: inline-block;
  padding: 11px 18px;
  border-radius: 10px;
  font-weight: 700;
  transition: 0.2s ease;
}

.btn:hover {
  transform: translateY(-1px);
  text-decoration: none;
}

.btn.primary {
  background: var(--accent);
  color: #2a2a2a;
}

.btn.secondary {
  background: rgba(255,255,255,0.16);
  color: #fff;
  border: 1px solid rgba(255,255,255,0.25);
}

.page-home,
.page-chapter {
  padding: 36px 0 56px;
}

.panel {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px;
  box-shadow: var(--shadow);
  margin-bottom: 22px;
}

.feature-list,
.roadmap {
  padding-left: 22px;
}

.chapter-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 14px;
}

.card {
  display: block;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 14px;
  padding: 18px;
  box-shadow: var(--shadow);
}

.card strong {
  display: block;
  margin-bottom: 6px;
}

.card span {
  color: var(--muted);
}

.chapter-layout {
  display: grid;
  grid-template-columns: 280px 1fr;
  gap: 24px;
}

.sidebar {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 18px;
  box-shadow: var(--shadow);
  height: fit-content;
  position: sticky;
  top: 84px;
}

.sidebar h2 {
  font-size: 1.05rem;
  margin-top: 0;
}

.sidebar nav {
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.sidebar nav a {
  padding: 8px 10px;
  border-radius: 10px;
}

.sidebar nav a.active,
.sidebar nav a:hover {
  background: var(--primary-light);
  text-decoration: none;
}

.content {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 30px;
  box-shadow: var(--shadow);
}

.content h1,
.content h2,
.content h3 {
  line-height: 1.35;
}

.content pre {
  background: var(--code-bg);
  color: var(--code-text);
  padding: 16px;
  border-radius: 12px;
  overflow-x: auto;
  font-size: 0.95rem;
}

.content code {
  font-family: Consolas, Monaco, monospace;
}

.note,
.warning,
.exercise {
  border-radius: 12px;
  padding: 16px 18px;
  margin: 18px 0;
}

.note {
  background: #eef5ff;
  border: 1px solid #cfe0f6;
}

.warning {
  background: #fff6e8;
  border: 1px solid #f0d7a8;
}

.exercise {
  background: #eefaf1;
  border: 1px solid #cfe8d6;
}

/* ===== 首頁 ===== */
.home-grid {
  display: grid;
  grid-template-columns: 1fr 480px;
  gap: 22px;
  align-items: start;
}

.roadmap {
  list-style: none;
  padding-left: 0;
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.roadmap li {
  display: flex;
  align-items: center;
  gap: 10px;
}

.roadmap-tag {
  display: inline-block;
  padding: 2px 10px;
  border-radius: 999px;
  font-size: 0.78rem;
  font-weight: 700;
  white-space: nowrap;
  background: var(--border);
  color: var(--muted);
}

.roadmap-tag.done {
  background: #d1fae5;
  color: #065f46;
}

.roadmap-tag.upcoming {
  background: var(--primary-light);
  color: var(--primary);
}

.toc-panel {
  padding: 24px;
}

.toc-list {
  list-style: none;
  padding: 0;
  margin: 0;
  display: flex;
  flex-direction: column;
  gap: 4px;
}

.toc-item a {
  display: flex;
  align-items: flex-start;
  gap: 14px;
  padding: 12px 14px;
  border-radius: 10px;
  transition: background 0.15s;
  color: var(--text);
}

.toc-item a:hover {
  background: var(--primary-light);
  text-decoration: none;
}

.toc-item.done a {
  color: var(--primary);
}

.toc-num {
  flex-shrink: 0;
  width: 28px;
  height: 28px;
  border-radius: 8px;
  background: var(--bg);
  border: 1px solid var(--border);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 0.78rem;
  font-weight: 700;
  color: var(--muted);
}

.toc-item.done .toc-num {
  background: var(--primary);
  border-color: var(--primary);
  color: #fff;
}

.toc-info {
  display: flex;
  flex-direction: column;
  gap: 2px;
}

.toc-info strong {
  font-size: 0.95rem;
  line-height: 1.4;
}

.toc-info span {
  font-size: 0.82rem;
  color: var(--muted);
}

@media (max-width: 900px) {
  .home-grid {
    grid-template-columns: 1fr;
  }
}

/* ===== 章節導覽 ===== */
.chapter-nav {
  display: flex;
  justify-content: space-between;
  gap: 12px;
  margin-top: 30px;
  flex-wrap: wrap;
}

.chapter-nav a {
  background: var(--primary);
  color: #fff;
  padding: 10px 16px;
  border-radius: 10px;
}

.site-footer {
  border-top: 1px solid var(--border);
  background: #fff;
  padding: 24px 0;
  color: var(--muted);
}

.back-top {
  position: fixed;
  right: 18px;
  bottom: 18px;
  display: none;
  background: var(--primary);
  color: #fff;
  border: none;
  border-radius: 999px;
  width: 44px;
  height: 44px;
  cursor: pointer;
  box-shadow: var(--shadow);
}

.back-top.show {
  display: inline-flex;
  align-items: center;
  justify-content: center;
}

@media (max-width: 900px) {
  .chapter-layout {
    grid-template-columns: 1fr;
  }

  .sidebar {
    position: static;
  }
}

@media (max-width: 720px) {
  .top-nav {
    display: none;
    position: absolute;
    right: 4%;
    top: 64px;
    background: #fff;
    border: 1px solid var(--border);
    border-radius: 12px;
    padding: 10px;
    box-shadow: var(--shadow);
    flex-direction: column;
    min-width: 180px;
  }

  .top-nav.open {
    display: flex;
  }

  .menu-toggle {
    display: inline-block;
  }

  .content,
  .panel,
  .sidebar {
    padding: 20px;
  }
}