/* ============================================================
   C++ 繁體中文教學網站 - 主要樣式表
   設計：深色主題 + 漸層 + 玻璃質感 + 響應式
============================================================ */

/* ===== CSS 變數：深色主題 ===== */
:root,
[data-theme="dark"] {
  --bg-primary: #0d1117;
  --bg-secondary: #161b22;
  --bg-tertiary: #21262d;
  --bg-card: #1c2128;
  --bg-code: #161b22;
  --bg-hover: #2d333b;

  --text-primary: #e6edf3;
  --text-secondary: #8b949e;
  --text-muted: #6e7681;
  --text-code: #e6edf3;
  --text-link: #58a6ff;

  --accent-blue: #58a6ff;
  --accent-purple: #bc8cff;
  --accent-green: #3fb950;
  --accent-orange: #d29922;
  --accent-red: #f85149;
  --accent-cyan: #39d353;
  --accent-pink: #f778ba;

  --border-color: #30363d;
  --border-hover: #484f58;
  --shadow: 0 8px 32px rgba(0,0,0,0.4);
  --shadow-lg: 0 20px 60px rgba(0,0,0,0.5);

  /* 代碼語法高亮 */
  --code-keyword: #ff7b72;
  --code-string: #a5d6ff;
  --code-comment: #8b949e;
  --code-number: #79c0ff;
  --code-func: #d2a8ff;
  --code-type: #ffa657;
  --code-preprocessor: #f0883e;
  --code-operator: #e6edf3;

  /* 漸層 */
  --grad-primary: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  --grad-blue: linear-gradient(135deg, #1a6bff 0%, #0052d4 100%);
  --grad-success: linear-gradient(135deg, #11998e 0%, #38ef7d 100%);
  --grad-hero: linear-gradient(135deg, #0d1117 0%, #1a1a2e 50%, #16213e 100%);
}

/* ===== CSS 變數：淺色主題 ===== */
[data-theme="light"] {
  --bg-primary: #ffffff;
  --bg-secondary: #f6f8fa;
  --bg-tertiary: #eaeef2;
  --bg-card: #ffffff;
  --bg-code: #f6f8fa;
  --bg-hover: #eaeef2;

  --text-primary: #24292f;
  --text-secondary: #57606a;
  --text-muted: #6e7781;
  --text-code: #24292f;
  --text-link: #0969da;

  --accent-blue: #0969da;
  --accent-purple: #8250df;
  --accent-green: #1a7f37;
  --accent-orange: #9a6700;
  --accent-red: #cf222e;
  --accent-cyan: #1b7c83;
  --accent-pink: #bf3989;

  --border-color: #d0d7de;
  --border-hover: #adb5bd;
  --shadow: 0 4px 16px rgba(0,0,0,0.1);
  --shadow-lg: 0 12px 40px rgba(0,0,0,0.15);

  --code-keyword: #cf222e;
  --code-string: #0a3069;
  --code-comment: #6e7781;
  --code-number: #0550ae;
  --code-func: #8250df;
  --code-type: #953800;
  --code-preprocessor: #953800;
  --code-operator: #24292f;

  --grad-hero: linear-gradient(135deg, #f0f4ff 0%, #e8f0fe 50%, #f0f7ff 100%);
}

/* ===== 全域重置 ===== */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

:root {
  --sidebar-width: 280px;
  --topnav-height: 60px;
  --transition: 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

html {
  scroll-behavior: smooth;
  font-size: 16px;
}

body {
  font-family: 'Noto Sans TC', -apple-system, BlinkMacSystemFont, sans-serif;
  background: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.7;
  overflow-x: hidden;
  transition: background var(--transition), color var(--transition);
}

/* ===== 自定義滾動條 ===== */
::-webkit-scrollbar { width: 6px; height: 6px; }
::-webkit-scrollbar-track { background: var(--bg-secondary); }
::-webkit-scrollbar-thumb {
  background: var(--border-hover);
  border-radius: 3px;
}
::-webkit-scrollbar-thumb:hover { background: var(--accent-blue); }

/* ===== 頂部導航欄 ===== */
.topnav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: var(--topnav-height);
  background: var(--bg-secondary);
  border-bottom: 1px solid var(--border-color);
  z-index: 1000;
  display: flex;
  align-items: center;
  padding: 0 16px;
  gap: 12px;
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  background: rgba(22, 27, 34, 0.92);
  transition: background var(--transition);
}

[data-theme="light"] .topnav {
  background: rgba(255,255,255,0.92);
}

.topnav-left { display: flex; align-items: center; gap: 10px; flex-shrink: 0; }
.topnav-center { flex: 1; max-width: 400px; position: relative; }
.topnav-right { display: flex; align-items: center; gap: 12px; margin-left: auto; flex-shrink: 0; }

.topnav-progress {
  position: absolute;
  bottom: 0;
  left: 0;
  right: 0;
  height: 2px;
  background: var(--border-color);
}

.topnav-progress-bar {
  height: 100%;
  background: var(--grad-primary);
  background: linear-gradient(90deg, var(--accent-blue), var(--accent-purple));
  transition: width 0.5s ease;
  width: 0%;
}

/* Hamburger Toggle */
.sidebar-toggle {
  width: 36px;
  height: 36px;
  background: none;
  border: none;
  cursor: pointer;
  display: flex;
  flex-direction: column;
  justify-content: center;
  gap: 5px;
  padding: 4px;
  border-radius: 6px;
  transition: background var(--transition);
}

.sidebar-toggle:hover { background: var(--bg-hover); }
.sidebar-toggle span {
  display: block;
  height: 2px;
  background: var(--text-secondary);
  border-radius: 2px;
  transition: transform var(--transition), opacity var(--transition);
}

/* Logo */
.logo {
  display: flex;
  align-items: center;
  gap: 8px;
  text-decoration: none;
  color: var(--text-primary);
  white-space: nowrap;
}

.logo-icon {
  background: var(--grad-primary);
  color: white;
  font-weight: 700;
  font-size: 12px;
  padding: 4px 8px;
  border-radius: 6px;
  letter-spacing: 0.5px;
  font-family: 'JetBrains Mono', monospace;
}

.logo-text {
  font-weight: 600;
  font-size: 15px;
  color: var(--text-primary);
}

/* Search Box */
.search-box {
  position: relative;
  width: 100%;
}

.search-icon {
  position: absolute;
  left: 10px;
  top: 50%;
  transform: translateY(-50%);
  width: 16px;
  height: 16px;
  color: var(--text-muted);
  pointer-events: none;
}

.search-box input {
  width: 100%;
  padding: 8px 12px 8px 34px;
  background: var(--bg-tertiary);
  border: 1px solid var(--border-color);
  border-radius: 20px;
  color: var(--text-primary);
  font-size: 13px;
  font-family: 'Noto Sans TC', sans-serif;
  outline: none;
  transition: border-color var(--transition), box-shadow var(--transition);
}

.search-box input:focus {
  border-color: var(--accent-blue);
  box-shadow: 0 0 0 3px rgba(88, 166, 255, 0.1);
}

.search-results {
  position: absolute;
  top: calc(100% + 4px);
  left: 0;
  right: 0;
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: 10px;
  box-shadow: var(--shadow);
  max-height: 300px;
  overflow-y: auto;
  z-index: 100;
  display: none;
}

.search-results.show { display: block; }

.search-result-item {
  padding: 10px 14px;
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 13px;
  border-bottom: 1px solid var(--border-color);
  transition: background var(--transition);
}

.search-result-item:last-child { border-bottom: none; }
.search-result-item:hover { background: var(--bg-hover); }
.search-result-item .result-num { color: var(--text-muted); font-size: 11px; font-family: 'JetBrains Mono', monospace; }
.search-result-item .result-title { font-weight: 500; }
.search-result-item .result-highlight { color: var(--accent-blue); background: rgba(88, 166, 255, 0.15); padding: 1px 3px; border-radius: 3px; }

/* Progress Info */
.progress-info {
  display: flex;
  flex-direction: column;
  align-items: flex-end;
  gap: 2px;
}

.progress-text { font-size: 10px; color: var(--text-muted); }
.progress-count { font-size: 12px; font-weight: 600; color: var(--accent-blue); font-family: 'JetBrains Mono', monospace; }

/* Theme Toggle */
.theme-toggle {
  width: 36px;
  height: 36px;
  border-radius: 50%;
  border: 1px solid var(--border-color);
  background: var(--bg-tertiary);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 16px;
  transition: all var(--transition);
  position: relative;
  overflow: hidden;
}

.theme-toggle:hover { border-color: var(--accent-blue); transform: scale(1.1); }

.theme-icon {
  position: absolute;
  transition: transform var(--transition), opacity var(--transition);
  line-height: 1;
}

[data-theme="dark"] .theme-icon.sun { transform: translateY(0); opacity: 1; }
[data-theme="dark"] .theme-icon.moon { transform: translateY(30px); opacity: 0; }
[data-theme="light"] .theme-icon.sun { transform: translateY(-30px); opacity: 0; }
[data-theme="light"] .theme-icon.moon { transform: translateY(0); opacity: 1; }

/* ===== 側欄 ===== */
.sidebar {
  position: fixed;
  top: var(--topnav-height);
  left: 0;
  width: var(--sidebar-width);
  height: calc(100vh - var(--topnav-height));
  background: var(--bg-secondary);
  border-right: 1px solid var(--border-color);
  overflow-y: auto;
  overflow-x: hidden;
  z-index: 900;
  transition: transform var(--transition);
  display: flex;
  flex-direction: column;
}

.sidebar-header {
  padding: 14px 16px;
  border-bottom: 1px solid var(--border-color);
  display: flex;
  align-items: center;
  justify-content: space-between;
  font-weight: 600;
  font-size: 13px;
  color: var(--text-secondary);
  flex-shrink: 0;
}

.sidebar-close {
  background: none;
  border: none;
  color: var(--text-muted);
  cursor: pointer;
  font-size: 14px;
  padding: 2px 6px;
  border-radius: 4px;
  display: none;
}

.sidebar-search {
  padding: 10px 12px;
  border-bottom: 1px solid var(--border-color);
  flex-shrink: 0;
}

.sidebar-search input {
  width: 100%;
  padding: 6px 10px;
  background: var(--bg-tertiary);
  border: 1px solid var(--border-color);
  border-radius: 6px;
  color: var(--text-primary);
  font-size: 12px;
  font-family: 'Noto Sans TC', sans-serif;
  outline: none;
  transition: border-color var(--transition);
}

.sidebar-search input:focus { border-color: var(--accent-blue); }

.sidebar-nav { flex: 1; overflow-y: auto; padding-bottom: 20px; }

/* Nav Groups */
.nav-group { border-bottom: 1px solid var(--border-color); }

.nav-group-title {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 10px 14px;
  cursor: pointer;
  font-size: 11px;
  font-weight: 700;
  letter-spacing: 0.5px;
  color: var(--text-muted);
  text-transform: uppercase;
  transition: background var(--transition), color var(--transition);
  user-select: none;
}

.nav-group-title:hover {
  background: var(--bg-hover);
  color: var(--text-primary);
}

.nav-group-title .chevron {
  width: 14px;
  height: 14px;
  transition: transform var(--transition);
  flex-shrink: 0;
}

.nav-group.collapsed .chevron { transform: rotate(-90deg); }
.nav-group.collapsed .nav-group-items { display: none; }

.nav-group-items {
  list-style: none;
  padding: 2px 0;
}

.nav-link {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 7px 14px 7px 20px;
  text-decoration: none;
  color: var(--text-secondary);
  font-size: 12.5px;
  transition: all var(--transition);
  position: relative;
  border-left: 2px solid transparent;
}

.nav-link:hover {
  color: var(--text-primary);
  background: var(--bg-hover);
  border-left-color: var(--accent-blue);
}

.nav-link.active {
  color: var(--accent-blue);
  background: rgba(88, 166, 255, 0.08);
  border-left-color: var(--accent-blue);
  font-weight: 500;
}

.nav-num {
  font-family: 'JetBrains Mono', monospace;
  font-size: 10px;
  color: var(--text-muted);
  min-width: 20px;
}

.nav-check {
  margin-left: auto;
  font-size: 10px;
  color: var(--accent-green);
  opacity: 0;
  transition: opacity var(--transition);
}

.nav-link.completed .nav-check { opacity: 1; }

/* Sidebar hidden/visible */
.sidebar-collapsed .sidebar {
  transform: translateX(calc(-1 * var(--sidebar-width)));
}

/* Sidebar Overlay */
.sidebar-overlay {
  display: none;
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: rgba(0,0,0,0.5);
  z-index: 800;
  backdrop-filter: blur(2px);
}

/* ===== 主內容區域 ===== */
.main-content {
  margin-left: var(--sidebar-width);
  margin-top: var(--topnav-height);
  min-height: calc(100vh - var(--topnav-height));
  transition: margin-left var(--transition);
  padding: 0;
}

.sidebar-collapsed .main-content { margin-left: 0; }

/* ===== HERO 區塊 ===== */
.hero-section {
  position: relative;
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 40px;
  align-items: center;
  padding: 80px 60px;
  min-height: 100vh;
  overflow: hidden;
  background: var(--grad-hero);
}

.hero-bg {
  position: absolute;
  inset: 0;
  background:
    radial-gradient(ellipse at 20% 50%, rgba(88, 166, 255, 0.08) 0%, transparent 60%),
    radial-gradient(ellipse at 80% 20%, rgba(188, 140, 255, 0.08) 0%, transparent 60%);
  pointer-events: none;
}

.hero-badge {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  background: rgba(88, 166, 255, 0.12);
  border: 1px solid rgba(88, 166, 255, 0.25);
  border-radius: 20px;
  padding: 5px 14px;
  font-size: 12px;
  color: var(--accent-blue);
  margin-bottom: 20px;
  animation: fadeInDown 0.6s ease;
}

.hero-title {
  font-size: clamp(2rem, 4vw, 3.5rem);
  font-weight: 900;
  line-height: 1.15;
  margin-bottom: 20px;
  animation: fadeInLeft 0.7s ease;
}

.gradient-text {
  background: linear-gradient(135deg, var(--accent-blue), var(--accent-purple));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero-desc {
  font-size: 16px;
  color: var(--text-secondary);
  margin-bottom: 32px;
  line-height: 1.8;
  animation: fadeInLeft 0.8s ease;
}

.hero-stats {
  display: flex;
  gap: 24px;
  margin-bottom: 32px;
  animation: fadeInLeft 0.9s ease;
}

.stat-item {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 2px;
}

.stat-num {
  font-size: 24px;
  font-weight: 900;
  font-family: 'JetBrains Mono', monospace;
  background: linear-gradient(135deg, var(--accent-blue), var(--accent-purple));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.stat-label {
  font-size: 11px;
  color: var(--text-muted);
  font-weight: 500;
}

.hero-actions {
  display: flex;
  gap: 12px;
  animation: fadeInLeft 1s ease;
}

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 10px 22px;
  border-radius: 8px;
  font-size: 14px;
  font-weight: 600;
  text-decoration: none;
  cursor: pointer;
  border: none;
  transition: all var(--transition);
  font-family: 'Noto Sans TC', sans-serif;
}

.btn-primary {
  background: linear-gradient(135deg, var(--accent-blue), #1a6bff);
  color: white;
  box-shadow: 0 4px 15px rgba(88, 166, 255, 0.3);
}

.btn-primary:hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 25px rgba(88, 166, 255, 0.4);
}

.btn-outline {
  background: transparent;
  color: var(--text-primary);
  border: 1px solid var(--border-color);
}

.btn-outline:hover {
  border-color: var(--accent-blue);
  color: var(--accent-blue);
  background: rgba(88, 166, 255, 0.08);
}

.btn-large { padding: 14px 32px; font-size: 16px; }

/* Code Window */
.hero-code {
  animation: fadeInRight 0.9s ease;
}

.code-window {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: 12px;
  overflow: hidden;
  box-shadow: var(--shadow-lg);
}

.code-window-header {
  background: var(--bg-tertiary);
  padding: 10px 16px;
  display: flex;
  align-items: center;
  gap: 10px;
  border-bottom: 1px solid var(--border-color);
}

.dot {
  width: 12px;
  height: 12px;
  border-radius: 50%;
}
.dot.red { background: #ff5f57; }
.dot.yellow { background: #febc2e; }
.dot.green { background: #28c840; }

.code-window-title {
  font-family: 'JetBrains Mono', monospace;
  font-size: 12px;
  color: var(--text-muted);
  margin-left: auto;
}

.code-window-body {
  padding: 20px;
  font-family: 'JetBrains Mono', monospace;
  font-size: 13px;
  line-height: 1.7;
  overflow: auto;
  max-height: 420px;
}

.code-window-body pre { white-space: pre-wrap; word-break: break-word; }

/* ===== 章節概覽卡片 ===== */
.section {
  padding: 60px;
  border-bottom: 1px solid var(--border-color);
  transition: background var(--transition);
}

.section:hover { background: var(--bg-secondary); }
.section:last-child { border-bottom: none; }

.chapters-overview {
  background: var(--bg-secondary);
  padding: 60px;
}

.section-header {
  text-align: center;
  margin-bottom: 40px;
}

.section-header h2 {
  font-size: 28px;
  font-weight: 800;
  margin-bottom: 8px;
}

.section-header p {
  color: var(--text-secondary);
  font-size: 15px;
}

.chapter-cards {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 20px;
}

.chapter-card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: 12px;
  padding: 20px;
  cursor: pointer;
  display: flex;
  align-items: flex-start;
  gap: 16px;
  transition: all var(--transition);
  position: relative;
  overflow: hidden;
}

.chapter-card::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 3px;
  background: var(--grad-primary);
  transform: scaleX(0);
  transition: transform var(--transition);
  transform-origin: left;
}

.chapter-card:hover {
  border-color: var(--accent-blue);
  transform: translateY(-4px);
  box-shadow: var(--shadow);
}

.chapter-card:hover::before { transform: scaleX(1); }

.chapter-card-icon {
  font-size: 28px;
  flex-shrink: 0;
  width: 48px;
  height: 48px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--bg-hover);
  border-radius: 10px;
}

.chapter-card-info h3 {
  font-size: 15px;
  font-weight: 700;
  margin-bottom: 4px;
}

.chapter-card-info p {
  font-size: 12px;
  color: var(--text-muted);
  margin-bottom: 8px;
}

.chapter-card-count {
  font-size: 11px;
  background: rgba(88, 166, 255, 0.12);
  color: var(--accent-blue);
  padding: 2px 8px;
  border-radius: 10px;
}

/* ===== 章節標題樣式 ===== */
.section-label {
  font-size: 11px;
  font-weight: 700;
  letter-spacing: 1px;
  text-transform: uppercase;
  color: var(--accent-blue);
  margin-bottom: 8px;
  font-family: 'JetBrains Mono', monospace;
}

.section-title {
  font-size: clamp(20px, 3vw, 28px);
  font-weight: 800;
  margin-bottom: 16px;
  line-height: 1.3;
}

.section-intro {
  font-size: 15px;
  color: var(--text-secondary);
  margin-bottom: 28px;
  max-width: 800px;
  line-height: 1.8;
}

/* ===== 代碼區塊 ===== */
.code-block {
  background: var(--bg-code);
  border: 1px solid var(--border-color);
  border-radius: 10px;
  overflow: hidden;
  margin: 20px 0;
  position: relative;
}

.code-header {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 8px 14px;
  background: var(--bg-tertiary);
  border-bottom: 1px solid var(--border-color);
}

.code-lang-badge {
  font-family: 'JetBrains Mono', monospace;
  font-size: 11px;
  font-weight: 700;
  padding: 2px 8px;
  border-radius: 5px;
  background: rgba(88, 166, 255, 0.15);
  color: var(--accent-blue);
  letter-spacing: 0.5px;
}

.code-lang-badge.error {
  background: rgba(248, 81, 73, 0.15);
  color: var(--accent-red);
}

.code-lang-badge.success {
  background: rgba(63, 185, 80, 0.15);
  color: var(--accent-green);
}

.code-filename {
  font-family: 'JetBrains Mono', monospace;
  font-size: 11px;
  color: var(--text-muted);
}

.copy-btn {
  margin-left: auto;
  background: var(--bg-hover);
  border: 1px solid var(--border-color);
  color: var(--text-secondary);
  padding: 4px 10px;
  border-radius: 5px;
  cursor: pointer;
  font-size: 11px;
  font-family: 'Noto Sans TC', sans-serif;
  transition: all var(--transition);
  white-space: nowrap;
}

.copy-btn:hover {
  background: var(--accent-blue);
  color: white;
  border-color: var(--accent-blue);
}

.copy-btn.copied {
  background: var(--accent-green);
  color: white;
  border-color: var(--accent-green);
}

.code-block pre {
  padding: 16px 18px;
  overflow-x: auto;
  font-size: 13.5px;
  line-height: 1.65;
}

.code-block code {
  font-family: 'JetBrains Mono', monospace;
  color: var(--text-code);
  white-space: pre;
}

/* Syntax Highlighting Classes */
.kw   { color: var(--code-keyword); font-weight: 600; }
.str  { color: var(--code-string); }
.cmt  { color: var(--code-comment); font-style: italic; }
.num  { color: var(--code-number); }
.fn   { color: var(--code-func); }
.typ  { color: var(--code-type); }
.pre  { color: var(--code-preprocessor); }
.op   { color: var(--code-operator); }

/* 代碼輸出框 */
.code-output-box {
  background: var(--bg-primary);
  border-top: 1px solid var(--border-color);
}

.output-header {
  padding: 8px 16px;
  font-size: 11px;
  font-weight: 700;
  color: var(--accent-green);
  background: rgba(63, 185, 80, 0.05);
  border-bottom: 1px dashed var(--border-color);
  font-family: 'JetBrains Mono', monospace;
}

.output-content {
  padding: 12px 16px;
  font-family: 'JetBrains Mono', monospace;
  font-size: 12.5px;
  color: var(--accent-green);
  white-space: pre;
  line-height: 1.7;
  overflow-x: auto;
}

/* Inline code */
code {
  font-family: 'JetBrains Mono', monospace;
  background: rgba(88, 166, 255, 0.1);
  color: var(--accent-blue);
  padding: 1px 5px;
  border-radius: 4px;
  font-size: 0.875em;
}

.code-block code { background: none; padding: 0; border-radius: 0; }

/* ===== 提示框 ===== */
.alert {
  display: flex;
  align-items: flex-start;
  gap: 12px;
  padding: 14px 18px;
  border-radius: 10px;
  margin: 16px 0;
  border-left: 4px solid;
  font-size: 14px;
  line-height: 1.7;
}

.alert-icon { font-size: 18px; flex-shrink: 0; margin-top: 1px; }

.alert-tip {
  background: rgba(63, 185, 80, 0.08);
  border-color: var(--accent-green);
  color: var(--text-primary);
}

.alert-warning {
  background: rgba(210, 153, 34, 0.1);
  border-color: var(--accent-orange);
  color: var(--text-primary);
}

.alert-info {
  background: rgba(88, 166, 255, 0.08);
  border-color: var(--accent-blue);
  color: var(--text-primary);
}

.alert-error {
  background: rgba(248, 81, 73, 0.08);
  border-color: var(--accent-red);
  color: var(--text-primary);
}

/* ===== 資訊卡片 ===== */
.info-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
  gap: 16px;
  margin: 20px 0;
}

.info-card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: 10px;
  padding: 18px;
  transition: all var(--transition);
  position: relative;
  overflow: hidden;
}

.info-card:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow);
}

.info-card::after {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 3px;
}

.info-card.accent-blue::after { background: var(--accent-blue); }
.info-card.accent-purple::after { background: var(--accent-purple); }
.info-card.accent-green::after { background: var(--accent-green); }
.info-card.accent-orange::after { background: var(--accent-orange); }

.info-card-icon { font-size: 24px; margin-bottom: 10px; }
.info-card h4 { font-size: 14px; font-weight: 700; margin-bottom: 6px; }
.info-card p { font-size: 12px; color: var(--text-secondary); line-height: 1.6; }
.info-card a { color: var(--accent-blue); text-decoration: none; }
.info-card a:hover { text-decoration: underline; }

/* ===== 應用網格 ===== */
.application-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(250px, 1fr));
  gap: 12px;
  margin: 16px 0;
}

.app-item {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: 8px;
  padding: 14px 16px;
  display: flex;
  align-items: flex-start;
  gap: 12px;
  transition: all var(--transition);
}

.app-item:hover {
  border-color: var(--accent-blue);
  background: rgba(88, 166, 255, 0.04);
}

.app-icon { font-size: 20px; flex-shrink: 0; }
.app-name { font-weight: 600; font-size: 13px; display: block; }
.app-desc { font-size: 12px; color: var(--text-muted); margin-top: 2px; display: block; }

/* ===== 比較表格 ===== */
.table-container {
  overflow-x: auto;
  margin: 16px 0;
  border-radius: 10px;
  border: 1px solid var(--border-color);
}

.data-table,
.comparison-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 13px;
}

.data-table th,
.comparison-table th {
  padding: 12px 16px;
  background: var(--bg-tertiary);
  font-weight: 700;
  text-align: left;
  white-space: nowrap;
  border-bottom: 1px solid var(--border-color);
  color: var(--text-secondary);
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 0.3px;
}

.data-table td,
.comparison-table td {
  padding: 10px 16px;
  border-bottom: 1px solid var(--border-color);
  line-height: 1.5;
}

.data-table tr:last-child td,
.comparison-table tr:last-child td { border-bottom: none; }

.data-table tr:hover td,
.comparison-table tr:hover td { background: var(--bg-hover); }

.cell-good { color: var(--accent-green); }
.cell-mid { color: var(--accent-orange); }
.cell-slow { color: var(--accent-red); }

/* ===== 步驟列表 ===== */
.steps-list { display: flex; flex-direction: column; gap: 16px; margin: 16px 0; }

.step-item {
  display: flex;
  gap: 16px;
  align-items: flex-start;
}

.step-num {
  width: 32px;
  height: 32px;
  background: var(--grad-primary);
  color: white;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 700;
  font-size: 13px;
  flex-shrink: 0;
  margin-top: 2px;
}

.step-body h4 { font-size: 14px; font-weight: 700; margin-bottom: 4px; }
.step-body p { font-size: 13px; color: var(--text-secondary); }

/* ===== 標籤頁 ===== */
.tabs-container { margin: 20px 0; }

.tabs-header {
  display: flex;
  gap: 4px;
  border-bottom: 1px solid var(--border-color);
  margin-bottom: 20px;
  overflow-x: auto;
  padding-bottom: 0;
}

.tab-btn {
  padding: 8px 16px;
  background: none;
  border: none;
  border-bottom: 2px solid transparent;
  color: var(--text-secondary);
  cursor: pointer;
  font-size: 13px;
  font-weight: 500;
  font-family: 'Noto Sans TC', sans-serif;
  white-space: nowrap;
  transition: all var(--transition);
  margin-bottom: -1px;
}

.tab-btn:hover { color: var(--text-primary); }
.tab-btn.active { color: var(--accent-blue); border-bottom-color: var(--accent-blue); }

.tab-content { display: none; }
.tab-content.active { display: block; animation: fadeIn 0.3s ease; }

/* ===== 規則網格 ===== */
.rules-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
  gap: 16px;
  margin: 16px 0;
}

.rule-card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: 10px;
  padding: 18px;
  text-align: center;
  transition: all var(--transition);
}

.rule-card:hover { border-color: var(--accent-blue); transform: translateY(-3px); }
.rule-icon { font-size: 28px; font-weight: 700; color: var(--accent-blue); margin-bottom: 8px; font-family: 'JetBrains Mono', monospace; }
.rule-card h4 { font-size: 13px; font-weight: 700; margin-bottom: 6px; }
.rule-card p { font-size: 12px; color: var(--text-secondary); }

/* ===== 錯誤對比 ===== */
.error-compare {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
  margin: 16px 0;
}

.error-header, .correct-header {
  padding: 8px 14px;
  font-size: 13px;
  font-weight: 700;
  border-radius: 6px 6px 0 0;
}

.error-header { background: rgba(248, 81, 73, 0.1); color: var(--accent-red); }
.correct-header { background: rgba(63, 185, 80, 0.1); color: var(--accent-green); }

/* ===== 命名規則 ===== */
.naming-rules {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
  margin: 16px 0;
}

.rule-item {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: 10px;
  padding: 16px;
}

.rule-item.allowed { border-color: rgba(63, 185, 80, 0.3); }
.rule-item.forbidden { border-color: rgba(248, 81, 73, 0.3); }

.rule-status {
  display: inline-block;
  padding: 3px 10px;
  border-radius: 12px;
  font-size: 11px;
  font-weight: 700;
  margin-bottom: 10px;
}

.allowed .rule-status { background: rgba(63, 185, 80, 0.15); color: var(--accent-green); }
.forbidden .rule-status { background: rgba(248, 81, 73, 0.15); color: var(--accent-red); }

.rule-item ul { list-style: none; }
.rule-item li { font-size: 12.5px; color: var(--text-secondary); padding: 3px 0; }

/* ===== 解釋列表 ===== */
.explanation-list { display: flex; flex-direction: column; gap: 12px; margin: 16px 0; }

.explain-item {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: 8px;
  padding: 14px 16px;
  border-left: 3px solid var(--accent-blue);
}

.explain-code {
  display: block;
  font-family: 'JetBrains Mono', monospace;
  font-size: 13px;
  color: var(--accent-blue);
  background: rgba(88, 166, 255, 0.1);
  padding: 4px 8px;
  border-radius: 5px;
  margin-bottom: 8px;
}

.explain-item p { font-size: 13px; color: var(--text-secondary); line-height: 1.7; }

/* ===== 測驗區塊 ===== */
.quiz-box {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: 12px;
  padding: 20px;
  margin: 24px 0;
  border-left: 4px solid var(--accent-purple);
}

.quiz-box h4 { font-size: 14px; font-weight: 700; color: var(--accent-purple); margin-bottom: 10px; }
.quiz-box p { font-size: 14px; margin-bottom: 14px; line-height: 1.7; }

.quiz-options { display: flex; flex-direction: column; gap: 8px; }

.quiz-opt {
  background: var(--bg-tertiary);
  border: 1px solid var(--border-color);
  color: var(--text-primary);
  padding: 10px 16px;
  border-radius: 7px;
  cursor: pointer;
  font-size: 13px;
  text-align: left;
  font-family: 'Noto Sans TC', sans-serif;
  transition: all var(--transition);
  line-height: 1.5;
}

.quiz-opt:hover:not(:disabled) {
  border-color: var(--accent-blue);
  background: rgba(88, 166, 255, 0.08);
}

.quiz-opt.correct {
  background: rgba(63, 185, 80, 0.15) !important;
  border-color: var(--accent-green) !important;
  color: var(--accent-green) !important;
  font-weight: 600;
}

.quiz-opt.wrong {
  background: rgba(248, 81, 73, 0.1) !important;
  border-color: var(--accent-red) !important;
  color: var(--accent-red) !important;
}

.quiz-opt:disabled { cursor: not-allowed; opacity: 0.7; }

.quiz-result {
  margin-top: 10px;
  font-size: 13px;
  font-weight: 600;
  padding: 8px 12px;
  border-radius: 6px;
  display: none;
}

.quiz-result.show { display: block; }
.quiz-result.correct-msg { background: rgba(63, 185, 80, 0.1); color: var(--accent-green); }
.quiz-result.wrong-msg { background: rgba(248, 81, 73, 0.1); color: var(--accent-red); }

/* ===== 完成按鈕 ===== */
.section-complete { margin-top: 30px; padding-top: 20px; border-top: 1px dashed var(--border-color); }

.btn-complete {
  background: none;
  border: 1px solid var(--border-color);
  color: var(--text-secondary);
  padding: 8px 18px;
  border-radius: 20px;
  cursor: pointer;
  font-size: 13px;
  font-family: 'Noto Sans TC', sans-serif;
  transition: all var(--transition);
}

.btn-complete:hover {
  border-color: var(--accent-green);
  color: var(--accent-green);
  background: rgba(63, 185, 80, 0.08);
}

.btn-complete.completed {
  background: rgba(63, 185, 80, 0.15);
  border-color: var(--accent-green);
  color: var(--accent-green);
  font-weight: 600;
}

/* ===== 標題 ===== */
h3 {
  font-size: 18px;
  font-weight: 700;
  margin: 28px 0 14px;
  color: var(--text-primary);
}

/* ===== 真值表 ===== */
.truth-tables {
  display: flex;
  gap: 20px;
  flex-wrap: wrap;
  margin: 16px 0;
}

.truth-table { flex: 1; min-width: 160px; }
.truth-table h4 { font-size: 14px; font-weight: 700; margin-bottom: 8px; font-family: 'JetBrains Mono', monospace; color: var(--accent-blue); }

/* ===== 最佳實踐 ===== */
.best-practices { display: grid; grid-template-columns: 1fr 1fr; gap: 16px; margin: 16px 0; }

.practice-item {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: 10px;
  padding: 16px;
  display: flex;
  gap: 12px;
}

.practice-item.good { border-color: rgba(63, 185, 80, 0.3); }
.practice-item.bad { border-color: rgba(248, 81, 73, 0.3); }

.practice-icon { font-size: 20px; flex-shrink: 0; }
.practice-item h4 { font-size: 13px; font-weight: 700; margin-bottom: 8px; }
.practice-item ul { list-style: none; }
.practice-item li { font-size: 12px; color: var(--text-secondary); padding: 2px 0; }

/* ===== 專案特性 ===== */
.project-features {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin: 16px 0;
}

.feature-item {
  background: rgba(63, 185, 80, 0.1);
  color: var(--accent-green);
  border: 1px solid rgba(63, 185, 80, 0.2);
  padding: 5px 12px;
  border-radius: 20px;
  font-size: 12px;
  font-weight: 500;
}

/* ===== 大型測驗 ===== */
.mega-quiz { max-width: 800px; }

.quiz-progress-bar {
  height: 6px;
  background: var(--bg-tertiary);
  border-radius: 3px;
  margin-bottom: 16px;
  overflow: hidden;
}

.quiz-progress-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--accent-blue), var(--accent-purple));
  border-radius: 3px;
  transition: width 0.5s ease;
  width: 0%;
}

.quiz-score-display {
  text-align: right;
  font-size: 13px;
  color: var(--text-muted);
  margin-bottom: 20px;
  font-family: 'JetBrains Mono', monospace;
}

.mega-quiz-item {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: 12px;
  padding: 20px;
  margin-bottom: 16px;
  transition: border-color var(--transition);
}

.mega-quiz-item.answered { border-color: var(--accent-blue); }

.mq-num {
  font-size: 11px;
  font-weight: 700;
  color: var(--accent-blue);
  letter-spacing: 0.5px;
  text-transform: uppercase;
  font-family: 'JetBrains Mono', monospace;
  margin-bottom: 8px;
}

.mq-question {
  font-size: 14px;
  font-weight: 600;
  margin-bottom: 14px;
  line-height: 1.7;
}

.mq-options { display: flex; flex-direction: column; gap: 8px; }

.mq-opt {
  background: var(--bg-tertiary);
  border: 1px solid var(--border-color);
  color: var(--text-primary);
  padding: 10px 16px;
  border-radius: 7px;
  cursor: pointer;
  font-size: 13px;
  text-align: left;
  font-family: 'Noto Sans TC', sans-serif;
  transition: all var(--transition);
}

.mq-opt:hover:not(:disabled) {
  border-color: var(--accent-blue);
  background: rgba(88, 166, 255, 0.08);
}

.mq-opt.selected { border-color: var(--accent-blue); background: rgba(88, 166, 255, 0.1); }
.mq-opt.correct-ans { background: rgba(63, 185, 80, 0.15); border-color: var(--accent-green); color: var(--accent-green); font-weight: 600; }
.mq-opt.wrong-ans { background: rgba(248, 81, 73, 0.1); border-color: var(--accent-red); color: var(--accent-red); }
.mq-opt:disabled { cursor: not-allowed; }

.mq-explain {
  margin-top: 10px;
  padding: 10px 14px;
  background: rgba(88, 166, 255, 0.06);
  border-radius: 7px;
  font-size: 12.5px;
  color: var(--text-secondary);
  line-height: 1.7;
  display: none;
  border-left: 3px solid var(--accent-blue);
}

.mq-explain.show { display: block; animation: fadeIn 0.3s ease; }

.quiz-final-result {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: 12px;
  padding: 24px;
  margin-top: 20px;
  text-align: center;
  display: none;
}

.quiz-final-result.show { display: block; animation: scaleIn 0.4s ease; }

.final-score {
  font-size: 60px;
  font-weight: 900;
  font-family: 'JetBrains Mono', monospace;
  background: linear-gradient(135deg, var(--accent-blue), var(--accent-purple));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  margin-bottom: 8px;
}

.final-grade { font-size: 18px; font-weight: 700; margin-bottom: 8px; }
.final-msg { font-size: 14px; color: var(--text-secondary); margin-bottom: 16px; }

/* ===== 回到頂部按鈕 ===== */
.back-to-top {
  position: fixed;
  bottom: 30px;
  right: 30px;
  width: 44px;
  height: 44px;
  background: var(--grad-primary);
  color: white;
  border: none;
  border-radius: 50%;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: 0 4px 15px rgba(88, 166, 255, 0.3);
  opacity: 0;
  transform: translateY(20px);
  transition: all var(--transition);
  z-index: 500;
}

.back-to-top.show { opacity: 1; transform: translateY(0); }
.back-to-top:hover { transform: translateY(-3px); box-shadow: 0 8px 25px rgba(88, 166, 255, 0.4); }
.back-to-top svg { width: 20px; height: 20px; }

/* ===== Footer ===== */
.footer {
  background: var(--bg-secondary);
  border-top: 1px solid var(--border-color);
  padding: 40px 60px 20px;
  margin-left: 0;
}

.sidebar-collapsed .footer { margin-left: 0; }

.footer-content {
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 40px;
  margin-bottom: 30px;
  max-width: 1200px;
}

.footer-logo {
  font-size: 18px;
  font-weight: 800;
  background: linear-gradient(135deg, var(--accent-blue), var(--accent-purple));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  margin-bottom: 8px;
}

.footer-brand p {
  font-size: 13px;
  color: var(--text-muted);
  max-width: 300px;
}

.footer-links { display: flex; gap: 40px; }

.footer-col { display: flex; flex-direction: column; gap: 8px; }
.footer-col h4 { font-size: 12px; font-weight: 700; text-transform: uppercase; letter-spacing: 0.5px; color: var(--text-muted); margin-bottom: 4px; }
.footer-col a { font-size: 13px; color: var(--text-secondary); text-decoration: none; transition: color var(--transition); }
.footer-col a:hover { color: var(--accent-blue); }

.footer-bottom {
  border-top: 1px solid var(--border-color);
  padding-top: 16px;
  text-align: center;
}

.footer-bottom p { font-size: 12px; color: var(--text-muted); }

/* ===== Toast 通知 ===== */
.toast {
  position: fixed;
  bottom: 80px;
  right: 30px;
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: 8px;
  padding: 10px 16px;
  font-size: 13px;
  box-shadow: var(--shadow);
  z-index: 2000;
  opacity: 0;
  transform: translateY(20px);
  transition: all var(--transition);
  pointer-events: none;
  max-width: 260px;
}

.toast.show { opacity: 1; transform: translateY(0); }
.toast.success { border-color: var(--accent-green); color: var(--accent-green); }
.toast.error { border-color: var(--accent-red); color: var(--accent-red); }

/* ===== KBD 鍵盤鍵 ===== */
kbd {
  background: var(--bg-tertiary);
  border: 1px solid var(--border-color);
  border-radius: 4px;
  padding: 2px 6px;
  font-family: 'JetBrains Mono', monospace;
  font-size: 11px;
  box-shadow: 0 1px 0 var(--border-color);
}

/* ===== Animations ===== */
@keyframes fadeIn { from { opacity: 0; } to { opacity: 1; } }
@keyframes fadeInDown { from { opacity: 0; transform: translateY(-20px); } to { opacity: 1; transform: translateY(0); } }
@keyframes fadeInLeft { from { opacity: 0; transform: translateX(-30px); } to { opacity: 1; transform: translateX(0); } }
@keyframes fadeInRight { from { opacity: 0; transform: translateX(30px); } to { opacity: 1; transform: translateX(0); } }
@keyframes scaleIn { from { opacity: 0; transform: scale(0.9); } to { opacity: 1; transform: scale(1); } }
@keyframes typing { from { width: 0; } to { width: 100%; } }
@keyframes pulse { 0%, 100% { opacity: 1; } 50% { opacity: 0.5; } }
@keyframes slideUp { from { opacity: 0; transform: translateY(30px); } to { opacity: 1; transform: translateY(0); } }

/* Section entrance animation */
.section { animation: slideUp 0.5s ease backwards; }

/* ===== 響應式設計 ===== */

/* 大螢幕（> 1400px） */
@media (min-width: 1400px) {
  .hero-section { padding: 100px 80px; }
  .section { padding: 70px 80px; }
}

/* 中等螢幕（< 1100px） */
@media (max-width: 1100px) {
  .hero-section { grid-template-columns: 1fr; padding: 60px 40px; min-height: auto; }
  .hero-code { display: none; }
  .section { padding: 40px 40px; }
  .footer { padding: 30px 40px 16px; }
}

/* 平板（< 768px） */
@media (max-width: 768px) {
  :root { --sidebar-width: 280px; }

  .sidebar {
    transform: translateX(calc(-1 * var(--sidebar-width)));
    box-shadow: var(--shadow-lg);
  }

  .sidebar.mobile-open {
    transform: translateX(0);
  }

  .sidebar-overlay.show { display: block; }

  .sidebar-close { display: flex; }

  .main-content { margin-left: 0 !important; }

  .sidebar-collapsed .main-content { margin-left: 0; }

  .hero-section { padding: 40px 24px; }
  .section { padding: 32px 24px; }
  .footer { padding: 24px 24px 16px; }

  .topnav-center { display: none; }

  .error-compare { grid-template-columns: 1fr; }
  .naming-rules { grid-template-columns: 1fr; }
  .best-practices { grid-template-columns: 1fr; }
  .truth-tables { flex-direction: column; }
  .footer-content { grid-template-columns: 1fr; }
  .footer-links { flex-wrap: wrap; gap: 24px; }

  .hero-stats { flex-wrap: wrap; gap: 16px; }
  .hero-actions { flex-wrap: wrap; }

  .chapter-cards { grid-template-columns: 1fr; }
  .info-grid { grid-template-columns: repeat(2, 1fr); }
  .rules-grid { grid-template-columns: repeat(2, 1fr); }
  .application-grid { grid-template-columns: 1fr; }
}

/* 手機（< 480px） */
@media (max-width: 480px) {
  .section { padding: 24px 16px; }
  .footer { padding: 20px 16px 12px; }

  .hero-section { padding: 30px 16px; }
  .hero-title { font-size: 1.8rem; }
  .hero-stats { gap: 12px; }

  .info-grid { grid-template-columns: 1fr; }
  .rules-grid { grid-template-columns: 1fr; }

  .logo-text { display: none; }
  .progress-info { display: none; }

  code { font-size: 0.78em; }
}

/* ===== 搜尋高亮 ===== */
mark {
  background: rgba(210, 153, 34, 0.3);
  color: var(--accent-orange);
  border-radius: 2px;
  padding: 0 2px;
}

/* ===== 圖片連結 ===== */
a { color: var(--text-link); transition: color var(--transition); }
a:hover { text-decoration: underline; }

/* ===== 選中文字顏色 ===== */
::selection {
  background: rgba(88, 166, 255, 0.25);
  color: var(--text-primary);
}

/* ===== 隱藏類 ===== */
.hidden { display: none !important; }
.nav-filtered .nav-link:not(.match) { display: none; }

/* ===== Print 樣式 ===== */
@media print {
  .topnav, .sidebar, .back-to-top, .footer, .quiz-box { display: none; }
  .main-content { margin: 0; }
  .section { break-inside: avoid; }
}

/* code-comment color in output */
.code-comment { color: var(--code-comment); font-style: italic; }
.code-output { color: var(--accent-green); }