/* ===========================================================
   AI 学习站 V2 - 深空主题
   =========================================================== */

:root {
  --bg-base: #0a0e1a;
  --bg-elevated: #131829;
  --bg-card: #1a2138;
  --bg-hover: #232b46;
  --bg-code: #0f1424;

  --text-primary: #e8ecf4;
  --text-secondary: #a8b2c8;
  --text-muted: #6c7693;
  --text-accent: #06b6d4;

  --accent-primary: #7c3aed;
  --accent-secondary: #06b6d4;
  --accent-tertiary: #f59e0b;
  --accent-success: #10b981;
  --accent-danger: #ef4444;

  --track-a: #3b82f6;     /* 蓝色 - Track A */
  --track-b: #f59e0b;     /* 橙色 - Track B */
  --track-hub: #8b5cf6;   /* 紫色 - 共用 hub */

  --border-base: #2a3354;
  --border-strong: #3d4870;

  --gradient-hero: linear-gradient(135deg, #7c3aed 0%, #06b6d4 50%, #f59e0b 100%);
  --gradient-card: linear-gradient(135deg, rgba(124, 58, 237, 0.08), rgba(6, 182, 212, 0.08));
  --gradient-button: linear-gradient(135deg, #7c3aed, #06b6d4);
  --gradient-track-a: linear-gradient(135deg, rgba(59, 130, 246, 0.15), rgba(59, 130, 246, 0.05));
  --gradient-track-b: linear-gradient(135deg, rgba(245, 158, 11, 0.15), rgba(245, 158, 11, 0.05));

  --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.3);
  --shadow-md: 0 8px 24px rgba(0, 0, 0, 0.4);
  --shadow-lg: 0 16px 48px rgba(0, 0, 0, 0.5);
  --shadow-glow: 0 0 32px rgba(124, 58, 237, 0.3);

  --radius-sm: 6px;
  --radius-md: 12px;
  --radius-lg: 20px;
  --radius-xl: 28px;

  --font-sans: -apple-system, BlinkMacSystemFont, "PingFang SC", "Microsoft YaHei", "Hiragino Sans GB", "Helvetica Neue", Arial, sans-serif;
  --font-mono: "JetBrains Mono", "Fira Code", Consolas, "Courier New", monospace;
}

[data-theme="light"] {
  --bg-base: #f8fafc;
  --bg-elevated: #ffffff;
  --bg-card: #ffffff;
  --bg-hover: #f1f5f9;
  --bg-code: #f1f5f9;
  --text-primary: #0f172a;
  --text-secondary: #475569;
  --text-muted: #94a3b8;
  --text-accent: #0891b2;
  --border-base: #e2e8f0;
  --border-strong: #cbd5e1;
  --gradient-card: linear-gradient(135deg, rgba(124, 58, 237, 0.05), rgba(8, 145, 178, 0.05));
  --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.06);
  --shadow-md: 0 8px 24px rgba(0, 0, 0, 0.08);
  --shadow-lg: 0 16px 48px rgba(0, 0, 0, 0.12);
  --shadow-glow: 0 0 32px rgba(124, 58, 237, 0.15);
}

*, *::before, *::after { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  font-family: var(--font-sans);
  background: var(--bg-base);
  color: var(--text-primary);
  line-height: 1.7;
  font-size: 16px;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  transition: background 0.3s, color 0.3s;
}
body.home-page { background: var(--bg-base); }
a { color: var(--text-accent); text-decoration: none; transition: color 0.2s; }
a:hover { color: var(--accent-primary); }
img { max-width: 100%; height: auto; }
code, pre { font-family: var(--font-mono); }
code { background: var(--bg-code); padding: 2px 6px; border-radius: 4px; font-size: 0.9em; color: var(--accent-tertiary); }
pre { background: var(--bg-code); padding: 16px; border-radius: var(--radius-md); overflow-x: auto; border: 1px solid var(--border-base); }
pre code { background: none; padding: 0; color: inherit; }
hr { border: none; border-top: 1px solid var(--border-base); margin: 32px 0; }

/* ===========================================================
   Topbar + Sidebar
   =========================================================== */
.topbar {
  position: sticky; top: 0; z-index: 100;
  background: rgba(10, 14, 26, 0.85);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  border-bottom: 1px solid var(--border-base);
  padding: 12px 24px;
  display: flex; align-items: center; justify-content: space-between; gap: 24px;
}
[data-theme="light"] .topbar { background: rgba(255, 255, 255, 0.85); }
.topbar-logo {
  font-size: 1.25rem; font-weight: 700;
  background: var(--gradient-hero);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  letter-spacing: -0.5px;
}
.topbar-nav { display: flex; gap: 4px; flex-wrap: wrap; }
.topbar-nav a {
  padding: 6px 14px;
  border-radius: var(--radius-sm);
  color: var(--text-secondary);
  font-size: 0.9rem;
  font-weight: 500;
  transition: all 0.2s;
}
.topbar-nav a:hover { background: var(--bg-hover); color: var(--text-primary); }
.topbar-nav a.active { background: var(--accent-primary); color: white; }
.topbar-actions { display: flex; gap: 8px; align-items: center; }
.theme-toggle, .search-toggle {
  background: var(--bg-card);
  border: 1px solid var(--border-base);
  color: var(--text-secondary);
  width: 36px; height: 36px;
  border-radius: var(--radius-sm);
  cursor: pointer;
  display: flex; align-items: center; justify-content: center;
  font-size: 1rem;
  transition: all 0.2s;
}
.theme-toggle:hover, .search-toggle:hover { background: var(--bg-hover); color: var(--text-primary); }

.layout { display: flex; max-width: 1400px; margin: 0 auto; min-height: calc(100vh - 60px); }
.sidebar {
  width: 280px;
  flex-shrink: 0;
  border-right: 1px solid var(--border-base);
  padding: 24px 16px;
  position: sticky;
  top: 60px;
  height: calc(100vh - 60px);
  overflow-y: auto;
}
.sidebar-group { margin-bottom: 16px; }
.sidebar-group-title {
  font-size: 0.75rem; font-weight: 700;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 1px;
  padding: 8px 12px;
  margin-bottom: 4px;
}
.sidebar-item {
  display: flex; align-items: center; gap: 8px;
  padding: 8px 12px;
  border-radius: var(--radius-sm);
  color: var(--text-secondary);
  font-size: 0.9rem;
  transition: all 0.2s;
  cursor: pointer;
}
.sidebar-item:hover { background: var(--bg-hover); color: var(--text-primary); }
.sidebar-item.active {
  background: var(--gradient-card);
  color: var(--text-accent);
  border-left: 3px solid var(--accent-primary);
  padding-left: 9px;
}
.sidebar-item .progress-dot {
  width: 8px; height: 8px;
  border-radius: 50%;
  background: var(--border-strong);
  flex-shrink: 0;
  margin-left: auto;
}
.sidebar-item.completed .progress-dot {
  background: var(--accent-success);
  box-shadow: 0 0 8px var(--accent-success);
}

.main {
  flex: 1;
  padding: 32px 48px;
  min-width: 0;
}

/* ===========================================================
   Hero 区
   =========================================================== */
.hero {
  position: relative;
  padding: 48px 0 32px;
  border-bottom: 1px solid var(--border-base);
  margin-bottom: 32px;
}
.hero::before {
  content: "";
  position: absolute;
  inset: 0;
  background:
    radial-gradient(ellipse at top right, rgba(124, 58, 237, 0.2), transparent 50%),
    radial-gradient(ellipse at bottom left, rgba(6, 182, 212, 0.15), transparent 50%);
  pointer-events: none;
}
.hero-title {
  font-size: 2.75rem;
  font-weight: 800;
  margin: 16px 0 16px;
  background: var(--gradient-hero);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  letter-spacing: -1.5px;
  position: relative;
  line-height: 1.2;
}
.hero-subtitle {
  font-size: 1.125rem;
  color: var(--text-secondary);
  margin: 0 0 24px;
  position: relative;
  max-width: 720px;
}
.hero-badge {
  display: inline-block;
  padding: 4px 14px;
  background: var(--bg-card);
  border: 1px solid var(--border-strong);
  border-radius: 20px;
  font-size: 0.8rem;
  color: var(--text-accent);
  font-weight: 600;
  letter-spacing: 1px;
  position: relative;
}

/* 首页 Hero - 居中版 */
.hero-home {
  text-align: center;
  padding: 64px 0 48px;
}
.hero-home .hero-title { font-size: 3.5rem; margin-top: 16px; }
.hero-home .hero-subtitle { margin-left: auto; margin-right: auto; font-size: 1.25rem; }
.hero-cta {
  display: flex;
  justify-content: center;
  gap: 16px;
  margin: 32px 0;
  flex-wrap: wrap;
  position: relative;
}
.hero-stats {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(120px, 1fr));
  gap: 16px;
  max-width: 700px;
  margin: 40px auto 0;
  position: relative;
}
.hero-stat {
  background: var(--bg-card);
  border: 1px solid var(--border-base);
  border-radius: var(--radius-md);
  padding: 16px;
}
.hero-stat .num {
  display: block;
  font-size: 2rem;
  font-weight: 800;
  background: var(--gradient-hero);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}
.hero-stat .label {
  display: block;
  font-size: 0.85rem;
  color: var(--text-muted);
  margin-top: 4px;
}

/* Stage 页 Hero */
.hero-stage .hero-stage-meta {
  display: flex; gap: 12px; align-items: center;
  margin-bottom: 16px;
  flex-wrap: wrap;
  position: relative;
}

/* ===========================================================
   按钮
   =========================================================== */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 12px 28px;
  border-radius: var(--radius-md);
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.25s;
  border: 1px solid transparent;
  text-decoration: none;
  font-family: inherit;
}
.btn-primary {
  background: var(--gradient-button);
  color: white;
  box-shadow: 0 4px 16px rgba(124, 58, 237, 0.4);
}
.btn-primary:hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 24px rgba(124, 58, 237, 0.5);
  color: white;
}
.btn-secondary {
  background: var(--bg-card);
  border-color: var(--border-strong);
  color: var(--text-primary);
}
.btn-secondary:hover {
  border-color: var(--accent-primary);
  background: var(--bg-hover);
  color: var(--text-primary);
}
.btn-large {
  padding: 16px 40px;
  font-size: 1.125rem;
}

/* ===========================================================
   区块标题
   =========================================================== */
.section { margin-bottom: 56px; }
.section-header {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  margin-bottom: 24px;
  padding-bottom: 12px;
  border-bottom: 1px solid var(--border-base);
}
.section-title {
  font-size: 1.75rem;
  font-weight: 700;
  margin: 0;
}
.section-subtitle {
  font-size: 0.875rem;
  color: var(--text-muted);
}

/* ===========================================================
   首页 - 项目介绍卡片
   =========================================================== */
.intro-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 16px;
}
.intro-card {
  background: var(--bg-card);
  border: 1px solid var(--border-base);
  border-radius: var(--radius-md);
  padding: 24px;
  transition: all 0.2s;
  position: relative;
  overflow: hidden;
}
.intro-card::before {
  content: "";
  position: absolute;
  inset: 0;
  background: var(--gradient-card);
  opacity: 0.4;
  pointer-events: none;
}
.intro-card:hover {
  border-color: var(--accent-primary);
  transform: translateY(-2px);
}
.intro-icon {
  font-size: 2.5rem;
  margin-bottom: 12px;
  position: relative;
}
.intro-card h3 {
  font-size: 1.125rem;
  margin: 0 0 8px;
  position: relative;
}
.intro-card p {
  font-size: 0.9rem;
  color: var(--text-secondary);
  margin: 0;
  line-height: 1.6;
  position: relative;
}
.intro-card strong { color: var(--text-accent); }

/* ===========================================================
   首页 - 学习路径图（全景）
   =========================================================== */
.path-container {
  background: var(--bg-card);
  border: 1px solid var(--border-base);
  border-radius: var(--radius-lg);
  padding: 32px;
  text-align: center;
}
.path-image {
  width: 100%;
  height: auto;
  display: block;
  border-radius: var(--radius-md);
}
.path-caption {
  margin-top: 16px;
  color: var(--text-muted);
  font-size: 0.9rem;
  text-align: center;
}

/* ===========================================================
   首页 - 两条路线对比
   =========================================================== */
.track-compare {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
  gap: 20px;
}
.track-card {
  background: var(--bg-card);
  border: 1px solid var(--border-base);
  border-radius: var(--radius-lg);
  padding: 28px;
  position: relative;
  overflow: hidden;
  transition: all 0.2s;
}
.track-card::before {
  content: "";
  position: absolute;
  inset: 0;
  opacity: 0.5;
  pointer-events: none;
}
.track-a::before { background: var(--gradient-track-a); }
.track-b::before { background: var(--gradient-track-b); }
.track-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
}
.track-a { border-top: 3px solid var(--track-a); }
.track-b { border-top: 3px solid var(--track-b); }
.track-head {
  display: flex; align-items: center; gap: 12px;
  margin-bottom: 12px;
  position: relative;
}
.track-icon {
  width: 44px; height: 44px;
  background: var(--bg-elevated);
  border: 1px solid var(--border-base);
  border-radius: 12px;
  display: flex; align-items: center; justify-content: center;
  font-size: 1.5rem;
  font-weight: 700;
  font-family: var(--font-mono);
}
.track-a .track-icon { color: var(--track-a); border-color: var(--track-a); }
.track-b .track-icon { color: var(--track-b); border-color: var(--track-b); }
.track-card h3 { margin: 0; font-size: 1.25rem; position: relative; }
.track-desc {
  color: var(--text-secondary);
  margin: 12px 0;
  position: relative;
}
.track-desc strong { color: var(--text-accent); }
.track-stages {
  list-style: none;
  padding: 0;
  margin: 16px 0;
  position: relative;
}
.track-stages li {
  padding: 10px 14px;
  margin: 6px 0;
  background: var(--bg-elevated);
  border-radius: var(--radius-sm);
  font-size: 0.9rem;
  border-left: 3px solid var(--border-strong);
}
.track-a .track-stages li { border-left-color: var(--track-a); }
.track-b .track-stages li { border-left-color: var(--track-b); }
.track-stages li.hub {
  background: linear-gradient(135deg, rgba(139, 92, 246, 0.15), rgba(139, 92, 246, 0.05));
  border-left-color: var(--track-hub);
}
.track-time {
  margin: 16px 0;
  padding: 12px;
  background: var(--bg-elevated);
  border-radius: var(--radius-sm);
  text-align: center;
  font-size: 0.95rem;
  position: relative;
}
.track-time strong { color: var(--text-accent); }
.track-card .btn {
  width: 100%;
  margin-top: 8px;
  position: relative;
}

/* ===========================================================
   首页 - 分支卡片
   =========================================================== */
.branch-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
  gap: 12px;
  margin-top: 16px;
}
.branch-card {
  background: var(--bg-card);
  border: 1px solid var(--border-base);
  border-radius: var(--radius-md);
  padding: 16px;
  text-align: center;
  transition: all 0.2s;
  color: var(--text-primary);
}
.branch-card:hover {
  border-color: var(--accent-primary);
  transform: translateY(-2px);
  box-shadow: var(--shadow-glow);
  color: var(--text-primary);
}
.branch-icon { font-size: 2rem; margin-bottom: 4px; }
.branch-card h4 { margin: 4px 0; font-size: 1rem; }
.branch-card p { margin: 0; font-size: 0.8rem; color: var(--text-muted); }

/* ===========================================================
   首页 - 全部 Stage 卡片（重设计）
   =========================================================== */
.stages-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 16px;
}
.stage-card {
  background: var(--bg-card);
  border: 1px solid var(--border-base);
  border-radius: var(--radius-md);
  padding: 20px;
  transition: all 0.2s;
  color: var(--text-primary);
  display: flex;
  flex-direction: column;
  position: relative;
  overflow: hidden;
}
.stage-card::before {
  content: "";
  position: absolute;
  inset: 0;
  background: var(--gradient-card);
  opacity: 0.3;
  pointer-events: none;
}
.stage-card:hover {
  border-color: var(--accent-primary);
  transform: translateY(-2px);
  box-shadow: var(--shadow-glow);
  color: var(--text-primary);
}
.stage-card-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-size: 0.75rem;
  margin-bottom: 12px;
  position: relative;
}
.stage-badge {
  padding: 2px 10px;
  border-radius: 10px;
  font-weight: 600;
  font-size: 0.7rem;
}
.stage-badge-easy { background: rgba(16, 185, 129, 0.15); color: var(--accent-success); }
.stage-badge-medium { background: rgba(245, 158, 11, 0.15); color: var(--accent-tertiary); }
.stage-badge-hard { background: rgba(239, 68, 68, 0.15); color: var(--accent-danger); }
.stage-time { color: var(--text-muted); font-size: 0.75rem; }
.stage-card-num {
  font-family: var(--font-mono);
  font-size: 1.75rem;
  font-weight: 800;
  background: var(--gradient-hero);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  margin-bottom: 4px;
  position: relative;
}
.stage-card-title {
  font-size: 1.05rem;
  font-weight: 700;
  margin: 0 0 8px;
  position: relative;
}
.stage-card-desc {
  font-size: 0.85rem;
  color: var(--text-secondary);
  margin: 0 0 12px;
  flex: 1;
  position: relative;
  line-height: 1.5;
}
.stage-card-footer {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding-top: 12px;
  border-top: 1px solid var(--border-base);
  font-size: 0.8rem;
  position: relative;
}
.stage-subtitle { color: var(--text-muted); }
.stage-arrow {
  color: var(--accent-primary);
  font-size: 1.2rem;
  font-weight: 700;
  transition: transform 0.2s;
}
.stage-card:hover .stage-arrow { transform: translateX(4px); }
.stage-group-tag {
  padding: 2px 10px;
  background: var(--bg-elevated);
  border-radius: 10px;
  color: var(--text-secondary);
  font-size: 0.7rem;
  font-weight: 500;
}

/* ===========================================================
   首页 - 学习哲学
   =========================================================== */
.philosophy {
  display: flex;
  align-items: center;
  gap: 16px;
  flex-wrap: wrap;
  justify-content: center;
  margin: 24px 0;
}
.phil-step {
  background: var(--bg-card);
  border: 1px solid var(--border-base);
  border-radius: var(--radius-md);
  padding: 20px;
  text-align: center;
  flex: 1;
  min-width: 220px;
  max-width: 280px;
  transition: all 0.2s;
}
.phil-step:hover { border-color: var(--accent-primary); }
.phil-num {
  width: 36px; height: 36px;
  background: var(--gradient-button);
  color: white;
  border-radius: 50%;
  display: flex; align-items: center; justify-content: center;
  font-weight: 800;
  margin: 0 auto 12px;
  font-size: 1.1rem;
}
.phil-step h4 {
  margin: 0 0 8px;
  font-size: 1rem;
  color: var(--text-primary);
}
.phil-step p {
  margin: 0 0 12px;
  font-size: 0.85rem;
  color: var(--text-secondary);
}
.phil-tag {
  display: inline-block;
  padding: 2px 10px;
  background: var(--bg-elevated);
  border-radius: 10px;
  font-size: 0.7rem;
  color: var(--text-accent);
  font-weight: 600;
}
.phil-arrow {
  color: var(--accent-primary);
  font-size: 2rem;
  font-weight: 800;
}
.phil-note {
  text-align: center;
  color: var(--text-secondary);
  margin-top: 16px;
  font-size: 0.95rem;
}
.phil-note strong { color: var(--accent-tertiary); }

/* ===========================================================
   首页 - 最后召唤
   =========================================================== */
.final-cta {
  text-align: center;
  padding: 48px 24px;
  background: linear-gradient(135deg, rgba(124, 58, 237, 0.05), rgba(6, 182, 212, 0.05));
  border-radius: var(--radius-lg);
  border: 1px solid var(--border-base);
}
.final-cta .section-title { text-align: center; }
.final-text { color: var(--text-secondary); margin: 0 0 24px; font-size: 1.1rem; }
.final-tip { margin-top: 16px; color: var(--text-muted); font-size: 0.9rem; }

/* ===========================================================
   Stage 页内容
   =========================================================== */
.content { max-width: 900px; }
.content h1 {
  font-size: 2.25rem;
  margin-top: 0;
  background: var(--gradient-hero);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}
.content h2 {
  font-size: 1.5rem;
  margin-top: 40px;
  padding-top: 16px;
  border-top: 1px solid var(--border-base);
  color: var(--text-primary);
}
.content h3 { font-size: 1.25rem; margin-top: 32px; color: var(--text-primary); }
.content h4 { font-size: 1.05rem; margin-top: 24px; color: var(--text-primary); }
.content p { color: var(--text-secondary); }
.content strong { color: var(--text-primary); font-weight: 700; }
.content ul, .content ol { color: var(--text-secondary); padding-left: 24px; }
.content li { margin-bottom: 6px; }
.content blockquote {
  border-left: 4px solid var(--accent-primary);
  padding: 12px 18px;
  background: var(--gradient-card);
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  color: var(--text-secondary);
  margin: 16px 0;
}
.content table {
  width: 100%;
  border-collapse: collapse;
  margin: 16px 0;
  background: var(--bg-card);
  border-radius: var(--radius-md);
  overflow: hidden;
  border: 1px solid var(--border-base);
  font-size: 0.9rem;
}
.content th, .content td {
  padding: 12px 16px;
  text-align: left;
  border-bottom: 1px solid var(--border-base);
}
.content th {
  background: var(--bg-elevated);
  color: var(--text-primary);
  font-weight: 700;
  font-size: 0.8rem;
  text-transform: uppercase;
  letter-spacing: 0.5px;
}
.content tr:last-child td { border-bottom: none; }
.content tr:hover td { background: var(--bg-hover); }

/* ===========================================================
   进度追踪按钮组
   =========================================================== */
.progress-tracker {
  display: flex;
  align-items: center;
  gap: 12px;
  margin: 24px 0;
  padding: 16px 20px;
  background: var(--bg-card);
  border: 1px solid var(--border-base);
  border-radius: var(--radius-md);
  flex-wrap: wrap;
}
.progress-tracker-label { font-weight: 600; color: var(--text-primary); }
.progress-tracker-buttons { display: flex; gap: 8px; margin-left: auto; flex-wrap: wrap; }
.progress-btn {
  padding: 6px 14px;
  background: var(--bg-elevated);
  border: 1px solid var(--border-base);
  color: var(--text-secondary);
  border-radius: var(--radius-sm);
  cursor: pointer;
  font-size: 0.875rem;
  font-family: inherit;
  transition: all 0.2s;
}
.progress-btn:hover { background: var(--bg-hover); color: var(--text-primary); }
.progress-btn.active {
  background: var(--accent-primary);
  color: white;
  border-color: var(--accent-primary);
}
.progress-btn.completed {
  background: var(--accent-success);
  color: white;
  border-color: var(--accent-success);
}

/* ===========================================================
   上下节导航
   =========================================================== */
.stage-nav {
  display: flex;
  justify-content: space-between;
  gap: 16px;
  margin: 48px 0 24px;
  padding-top: 32px;
  border-top: 1px solid var(--border-base);
}
.nav-btn {
  display: flex;
  align-items: center;
  gap: 16px;
  padding: 16px 24px;
  background: var(--bg-card);
  border: 1px solid var(--border-base);
  border-radius: var(--radius-md);
  color: var(--text-primary);
  transition: all 0.2s;
  flex: 1;
  max-width: 340px;
}
.nav-btn:hover {
  border-color: var(--accent-primary);
  transform: translateY(-2px);
  box-shadow: var(--shadow-glow);
  color: var(--text-primary);
}
.nav-next { text-align: right; margin-left: auto; flex-direction: row-reverse; }
.nav-arrow {
  font-size: 1.5rem;
  color: var(--accent-primary);
  font-weight: 700;
}
.nav-label { font-size: 0.75rem; color: var(--text-muted); text-transform: uppercase; letter-spacing: 1px; }
.nav-title { font-size: 1rem; font-weight: 600; margin-top: 2px; }

/* ===========================================================
   页脚
   =========================================================== */
.footer {
  border-top: 1px solid var(--border-base);
  padding: 32px 24px;
  text-align: center;
  color: var(--text-muted);
  font-size: 0.875rem;
  background: var(--bg-elevated);
  margin-top: 48px;
}
.footer-icp {
  margin-top: 12px;
  display: flex;
  justify-content: center;
  align-items: center;
  gap: 8px;
  flex-wrap: wrap;
}
.footer-icp a {
  color: var(--text-muted);
  text-decoration: none;
  padding: 4px 10px;
  border: 1px solid var(--border-base);
  border-radius: var(--radius-sm);
  transition: all 0.2s;
}
.footer-icp a:hover { color: var(--text-primary); border-color: var(--accent-primary); }

/* ===========================================================
   搜索面板
   =========================================================== */
.search-panel {
  position: fixed;
  top: 60px; left: 0; right: 0;
  background: var(--bg-elevated);
  border-bottom: 1px solid var(--border-base);
  padding: 16px 24px;
  z-index: 99;
  display: none;
  box-shadow: var(--shadow-lg);
}
.search-panel.open { display: block; }
.search-input {
  width: 100%; max-width: 600px;
  margin: 0 auto; display: block;
  padding: 12px 16px;
  background: var(--bg-card);
  border: 1px solid var(--border-base);
  border-radius: var(--radius-md);
  color: var(--text-primary);
  font-size: 1rem;
  font-family: inherit;
}
.search-input:focus { outline: none; border-color: var(--accent-primary); }
.search-results { max-width: 600px; margin: 12px auto 0; }
.search-result {
  padding: 12px;
  border-radius: var(--radius-sm);
  cursor: pointer;
  color: var(--text-secondary);
}
.search-result:hover { background: var(--bg-hover); }
.search-result-title { color: var(--text-primary); font-weight: 600; }
.search-result-snippet { font-size: 0.875rem; margin-top: 4px; }

/* ===========================================================
   响应式
   =========================================================== */
@media (max-width: 900px) {
  .layout { flex-direction: column; }
  .sidebar { position: static; width: 100%; height: auto; border-right: none; border-bottom: 1px solid var(--border-base); }
  .main { padding: 24px 20px; }
  .hero-title { font-size: 2rem; }
  .hero-home .hero-title { font-size: 2.25rem; }
  .philosophy { flex-direction: column; }
  .phil-arrow { transform: rotate(90deg); }
  .stage-nav { flex-direction: column; }
  .nav-btn { max-width: 100%; }
}