/* ===== CSS RESET & VARIABLES ===== */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

:root {
  --primary: #3b82f6;
  --primary-dark: #1d4ed8;
  --primary-light: #60a5fa;
  --accent: #06b6d4;
  --bg: #ffffff;
  --bg-secondary: #f8fafc;
  --bg-card: #ffffff;
  --text: #1e293b;
  --text-secondary: #64748b;
  --text-muted: #94a3b8;
  --border: #e2e8f0;
  --shadow: 0 1px 3px rgba(0,0,0,0.08), 0 4px 12px rgba(0,0,0,0.05);
  --shadow-lg: 0 4px 20px rgba(0,0,0,0.1);
  --radius: 12px;
  --radius-sm: 8px;
  --nav-height: 64px;
  --sidebar-width: 240px;
  --font-body: 'Noto Sans SC', 'PingFang SC', 'Microsoft YaHei', -apple-system, sans-serif;
  --transition: 0.3s cubic-bezier(0.4,0,0.2,1);
}

[data-theme="dark"] {
  --bg: #0f172a;
  --bg-secondary: #1e293b;
  --bg-card: #1e293b;
  --text: #f1f5f9;
  --text-secondary: #94a3b8;
  --text-muted: #64748b;
  --border: #334155;
  --shadow: 0 1px 3px rgba(0,0,0,0.3), 0 4px 12px rgba(0,0,0,0.2);
  --shadow-lg: 0 4px 20px rgba(0,0,0,0.4);
}

html { scroll-behavior: smooth; }

body {
  font-family: var(--font-body);
  background: var(--bg);
  color: var(--text);
  line-height: 1.7;
  transition: background var(--transition), color var(--transition);
  overflow-x: hidden;
}

/* ===== SCROLLBAR ===== */
::-webkit-scrollbar { width: 6px; }
::-webkit-scrollbar-track { background: var(--bg-secondary); }
::-webkit-scrollbar-thumb { background: var(--border); border-radius: 3px; }
::-webkit-scrollbar-thumb:hover { background: var(--text-muted); }

/* ===== TOP NAVIGATION ===== */
.top-nav {
  position: fixed;
  top: 0; left: 0; right: 0;
  height: var(--nav-height);
  background: rgba(255,255,255,0.92);
  border-bottom: 1px solid var(--border);
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 32px;
  z-index: 100;
  backdrop-filter: blur(20px);
  transition: all var(--transition);
}
[data-theme="dark"] .top-nav { background: rgba(15,23,42,0.92); }

.nav-brand {
  display: flex;
  align-items: center;
  gap: 10px;
  text-decoration: none;
  color: var(--text);
  font-weight: 700;
  font-size: 1.2rem;
}
.nav-logo { width: 36px; height: 36px; }

.nav-links {
  display: flex;
  align-items: center;
  gap: 4px;
  list-style: none;
}
.nav-links a {
  text-decoration: none;
  color: var(--text-secondary);
  padding: 8px 16px;
  border-radius: var(--radius-sm);
  font-size: 0.9rem;
  font-weight: 500;
  transition: all var(--transition);
  display: flex;
  align-items: center;
  gap: 6px;
}
.nav-links a:hover, .nav-links a.active {
  color: var(--primary);
  background: var(--bg-secondary);
}
.nav-links a.active { font-weight: 600; }

.nav-controls {
  display: flex;
  align-items: center;
  gap: 8px;
}

.theme-toggle {
  width: 40px; height: 40px;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  background: var(--bg-card);
  color: var(--text-secondary);
  cursor: pointer;
  display: flex; align-items: center; justify-content: center;
  font-size: 1.1rem;
  transition: all var(--transition);
}
.theme-toggle:hover { border-color: var(--primary); color: var(--primary); transform: scale(1.05); }
.theme-toggle .sun { display: none; }
.theme-toggle .moon { display: block; }
[data-theme="dark"] .theme-toggle .sun { display: block; }
[data-theme="dark"] .theme-toggle .moon { display: none; }

.lang-toggle {
  padding: 6px 14px;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  background: var(--bg-card);
  color: var(--text-secondary);
  cursor: pointer;
  font-size: 0.8rem;
  font-weight: 600;
  font-family: var(--font-body);
  transition: all var(--transition);
  display: flex; align-items: center; gap: 4px;
}
.lang-toggle:hover { border-color: var(--primary); color: var(--primary); }

.mobile-menu-btn {
  display: none;
  width: 40px; height: 40px;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  background: var(--bg-card);
  color: var(--text);
  cursor: pointer;
  flex-direction: column;
  align-items: center; justify-content: center;
  gap: 4px;
}
.mobile-menu-btn span {
  width: 18px; height: 2px;
  background: currentColor;
  border-radius: 2px;
  transition: all var(--transition);
}

/* ===== LAYOUT ===== */
.layout {
  display: flex;
  padding-top: var(--nav-height);
  min-height: 100vh;
}

/* ===== SIDEBAR ===== */
.sidebar {
  width: var(--sidebar-width);
  position: fixed;
  top: var(--nav-height);
  left: 0; bottom: 0;
  background: var(--bg);
  border-right: 1px solid var(--border);
  padding: 24px 0;
  overflow-y: auto;
  transition: transform var(--transition), background var(--transition);
  z-index: 90;
}
.sidebar-section { padding: 0 16px; margin-bottom: 24px; }
.sidebar-section-title {
  font-size: 0.7rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 1.5px;
  color: var(--text-muted);
  margin-bottom: 8px;
  padding: 0 12px;
}
.sidebar-links { list-style: none; }
.sidebar-links a {
  display: flex; align-items: center; gap: 10px;
  padding: 10px 12px;
  border-radius: var(--radius-sm);
  text-decoration: none;
  color: var(--text-secondary);
  font-size: 0.88rem;
  font-weight: 500;
  transition: all var(--transition);
}
.sidebar-links a:hover { background: var(--bg-secondary); color: var(--text); }
.sidebar-links a.active {
  background: linear-gradient(135deg, rgba(59,130,246,0.12), rgba(6,182,212,0.08));
  color: var(--primary);
  font-weight: 600;
}
.sidebar-links a .icon { font-size: 1rem; width: 20px; text-align: center; flex-shrink: 0; }

/* ===== MAIN CONTENT ===== */
.main-content {
  flex: 1;
  margin-left: var(--sidebar-width);
  min-height: calc(100vh - var(--nav-height));
}

.page-content { padding: 48px; max-width: 900px; }
.page-content h1 {
  font-size: 2.2rem; font-weight: 800;
  margin-bottom: 32px; padding-bottom: 16px;
  border-bottom: 2px solid var(--border);
}
.page-content h2 {
  font-size: 1.5rem; font-weight: 700;
  margin: 40px 0 16px; padding-top: 16px;
}
.page-content h3 { font-size: 1.15rem; font-weight: 600; margin: 28px 0 12px; }
.page-content p { margin-bottom: 16px; color: var(--text-secondary); line-height: 1.8; }
.page-content ul, .page-content ol { margin: 16px 0 20px 24px; color: var(--text-secondary); }
.page-content li { margin-bottom: 10px; line-height: 1.7; }
.page-content a { color: var(--primary); text-decoration: none; }
.page-content a:hover { text-decoration: underline; }

.highlight-box {
  background: linear-gradient(135deg, rgba(59,130,246,0.08), rgba(6,182,212,0.05));
  border: 1px solid rgba(59,130,246,0.2);
  border-radius: var(--radius); padding: 20px 24px; margin: 24px 0;
}
.highlight-box p { margin: 0; color: var(--text) !important; }

.warning-box {
  background: rgba(251,191,36,0.1);
  border: 1px solid rgba(251,191,36,0.3);
  border-radius: var(--radius); padding: 16px 20px; margin: 20px 0;
  font-size: 0.9rem; color: var(--text-secondary);
}
.warning-box strong { color: #d97706; }

/* ===== HERO ===== */
.hero {
  min-height: calc(100vh - var(--nav-height));
  display: flex; flex-direction: column;
  align-items: center; justify-content: center;
  text-align: center;
  padding: 80px 24px;
  position: relative;
  background: linear-gradient(180deg, var(--bg) 0%, var(--bg-secondary) 100%);
}
.hero::before {
  content: '';
  position: absolute; top: -50%; left: -20%;
  width: 80%; height: 100%;
  background: radial-gradient(ellipse, rgba(59,130,246,0.06) 0%, transparent 70%);
  pointer-events: none;
}
.hero::after {
  content: '';
  position: absolute; bottom: -30%; right: -10%;
  width: 60%; height: 80%;
  background: radial-gradient(ellipse, rgba(6,182,212,0.05) 0%, transparent 70%);
  pointer-events: none;
}

.hero-badge {
  display: inline-flex; align-items: center; gap: 8px;
  padding: 8px 20px;
  background: linear-gradient(135deg, rgba(59,130,246,0.1), rgba(6,182,212,0.1));
  border: 1px solid rgba(59,130,246,0.2);
  border-radius: 100px;
  font-size: 0.85rem; color: var(--primary); font-weight: 600;
  margin-bottom: 32px;
  animation: pulse 3s ease-in-out infinite;
}
@keyframes pulse {
  0%, 100% { box-shadow: 0 0 0 0 rgba(59,130,246,0.15); }
  50% { box-shadow: 0 0 0 12px rgba(59,130,246,0); }
}

.hero h1 {
  font-size: clamp(2.5rem, 6vw, 4.5rem);
  font-weight: 800; line-height: 1.15;
  margin-bottom: 20px;
  background: linear-gradient(135deg, var(--text) 40%, var(--primary) 100%);
  -webkit-background-clip: text; -webkit-text-fill-color: transparent;
  background-clip: text;
  letter-spacing: -0.02em;
}
[data-theme="dark"] .hero h1 {
  background: linear-gradient(135deg, #f1f5f9 40%, var(--primary-light) 100%);
  -webkit-background-clip: text; background-clip: text;
}

.hero-sub { font-size: 1.2rem; color: var(--text-secondary); margin-bottom: 48px; max-width: 520px; }

.hero-actions { display: flex; gap: 16px; flex-wrap: wrap; justify-content: center; }

.btn {
  display: inline-flex; align-items: center; gap: 8px;
  padding: 14px 32px;
  border-radius: var(--radius);
  font-size: 0.95rem; font-weight: 600;
  text-decoration: none; cursor: pointer;
  border: none; font-family: var(--font-body);
  transition: all var(--transition);
}
.btn-primary {
  background: linear-gradient(135deg, var(--primary), var(--primary-dark));
  color: #fff; box-shadow: 0 4px 16px rgba(59,130,246,0.3);
}
.btn-primary:hover { transform: translateY(-2px); box-shadow: 0 8px 24px rgba(59,130,246,0.4); text-decoration: none; }
.btn-secondary {
  background: var(--bg-card); color: var(--text);
  border: 1px solid var(--border); box-shadow: var(--shadow);
}
.btn-secondary:hover { border-color: var(--primary); color: var(--primary); transform: translateY(-2px); text-decoration: none; }

/* ===== SECTIONS ===== */
.section { padding: 80px 48px; }
.section-header { text-align: center; margin-bottom: 56px; }
.section-header h2 { font-size: 2rem; font-weight: 700; margin-bottom: 12px; }
.section-header p { color: var(--text-secondary); font-size: 1.05rem; max-width: 480px; margin: 0 auto; }

/* ===== FEATURES GRID ===== */
.features-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 24px; max-width: 1100px; margin: 0 auto;
}
.feature-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 32px 28px;
  transition: all var(--transition);
  position: relative; overflow: hidden;
}
.feature-card::before {
  content: '';
  position: absolute; top: 0; left: 0; right: 0;
  height: 3px;
  background: linear-gradient(90deg, var(--primary), var(--accent));
  opacity: 0; transition: opacity var(--transition);
}
.feature-card:hover { transform: translateY(-4px); box-shadow: var(--shadow-lg); border-color: rgba(59,130,246,0.2); }
.feature-card:hover::before { opacity: 1; }

.feature-icon {
  width: 52px; height: 52px;
  border-radius: var(--radius-sm);
  background: linear-gradient(135deg, rgba(59,130,246,0.12), rgba(6,182,212,0.08));
  display: flex; align-items: center; justify-content: center;
  font-size: 1.4rem; margin-bottom: 20px;
}
.feature-card h3 { font-size: 1.1rem; font-weight: 700; margin-bottom: 10px; }
.feature-card p { color: var(--text-secondary); font-size: 0.9rem; line-height: 1.65; }

/* ===== DOWNLOAD ===== */
.download-section { margin: 32px 0; }
.download-card {
  background: var(--bg-card); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 24px 28px;
  margin-bottom: 20px; transition: all var(--transition);
}
.download-card:hover { border-color: rgba(59,130,246,0.3); box-shadow: var(--shadow); }
.download-card h3 { margin-top: 0; margin-bottom: 12px; font-size: 1.15rem; }
.download-links { display: flex; gap: 12px; flex-wrap: wrap; margin-top: 12px; }
.download-link {
  display: inline-flex; align-items: center; gap: 6px;
  padding: 10px 20px;
  background: linear-gradient(135deg, var(--primary), var(--primary-dark));
  color: #fff; text-decoration: none;
  border-radius: var(--radius-sm); font-size: 0.88rem; font-weight: 600;
  transition: all var(--transition);
}
.download-link:hover { transform: translateY(-2px); box-shadow: 0 4px 12px rgba(59,130,246,0.3); text-decoration: none; }
.download-link.secondary { background: var(--bg-secondary); color: var(--text); border: 1px solid var(--border); }
.download-link.secondary:hover { border-color: var(--primary); color: var(--primary); }
.platform-badge {
  display: inline-flex; align-items: center; gap: 6px;
  padding: 4px 12px;
  background: var(--bg-secondary);
  border-radius: 100px; font-size: 0.8rem; color: var(--text-secondary);
  margin-bottom: 12px;
}

/* ===== AIRPORT ===== */
.airport-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 20px; margin-top: 24px;
}
.airport-card {
  background: var(--bg-card); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 24px;
  transition: all var(--transition);
}
.airport-card:hover { transform: translateY(-3px); box-shadow: var(--shadow-lg); border-color: rgba(59,130,246,0.2); }
.airport-card h4 { font-size: 1rem; font-weight: 700; margin-bottom: 8px; }
.airport-card p { font-size: 0.85rem; margin-bottom: 12px; }
.airport-tags { display: flex; gap: 6px; flex-wrap: wrap; margin-bottom: 14px; }
.airport-tag {
  padding: 3px 10px;
  background: rgba(59,130,246,0.1);
  color: var(--primary); border-radius: 100px;
  font-size: 0.75rem; font-weight: 600;
}

/* ===== FRIEND LINKS ===== */
.friend-links-section { padding: 60px 48px; background: var(--bg-secondary); border-top: 1px solid var(--border); }
.friend-links-section h3 { font-size: 1.1rem; font-weight: 700; margin-bottom: 20px; color: var(--text-secondary); text-align: center; }
.friend-links { display: flex; flex-wrap: wrap; gap: 12px; justify-content: center; max-width: 1100px; margin: 0 auto; }
.friend-link {
  padding: 6px 16px; border-radius: 100px;
  background: var(--bg-card); border: 1px solid var(--border);
  color: var(--text-secondary); text-decoration: none;
  font-size: 0.82rem; font-weight: 500; transition: all var(--transition);
}
.friend-link:hover { border-color: var(--primary); color: var(--primary); background: rgba(59,130,246,0.06); text-decoration: none; }

/* ===== FOOTER ===== */
footer {
  background: var(--bg-secondary); border-top: 1px solid var(--border);
  padding: 40px 48px; text-align: center;
  color: var(--text-muted); font-size: 0.85rem;
  margin-left: var(--sidebar-width);
}
footer a { color: var(--text-muted); text-decoration: none; }
footer a:hover { color: var(--primary); }

/* ===== LANGUAGE LABELS ===== */
/* Base: show both, let context rules handle visibility */
.lang-zh, .lang-en { display: inline; }
[data-lang="zh"] .lang-zh { display: inline; }
[data-lang="zh"] .lang-en { display: none; }
[data-lang="en"]  .lang-zh { display: none; }
[data-lang="en"]  .lang-en { display: inline; }

/* Block-level (vp-doc content) - same pattern */
.lang-block { display: block; }
[data-lang="zh"] .lang-block.lang-zh { display: block; }
[data-lang="zh"] .lang-block.lang-en { display: none; }
[data-lang="en"]  .lang-block.lang-zh { display: none; }
[data-lang="en"]  .lang-block.lang-en { display: block; }

/* ===== DECORATIVE ===== */
.grid-bg {
  position: fixed; inset: 0;
  background-image:
    linear-gradient(var(--border) 1px, transparent 1px),
    linear-gradient(90deg, var(--border) 1px, transparent 1px);
  background-size: 60px 60px;
  opacity: 0.3; pointer-events: none; z-index: -1;
}
[data-theme="dark"] .grid-bg { opacity: 0.08; }

/* ===== ANIMATIONS ===== */
@keyframes fadeIn {
  from { opacity: 0; transform: translateY(12px); }
  to { opacity: 1; transform: translateY(0); }
}
@keyframes slideUp {
  from { opacity: 0; transform: translateY(24px); }
  to { opacity: 1; transform: translateY(0); }
}
.feature-card, .download-card, .airport-card, .hero-badge { animation: slideUp 0.6s ease both; }
.feature-card:nth-child(1) { animation-delay: 0.1s; }
.feature-card:nth-child(2) { animation-delay: 0.2s; }
.feature-card:nth-child(3) { animation-delay: 0.3s; }
.feature-card:nth-child(4) { animation-delay: 0.15s; }
.feature-card:nth-child(5) { animation-delay: 0.25s; }
.feature-card:nth-child(6) { animation-delay: 0.35s; }
.feature-card:nth-child(7) { animation-delay: 0.3s; }
.feature-card:nth-child(8) { animation-delay: 0.4s; }
.feature-card:nth-child(9) { animation-delay: 0.45s; }

/* ===== MOBILE SIDEBAR ===== */
.sidebar-overlay { display: none; position: fixed; inset: 0; background: rgba(0,0,0,0.5); z-index: 85; }
.sidebar-overlay.show { display: block; }

/* ===== RESPONSIVE ===== */
@media (max-width: 900px) {
  .sidebar { transform: translateX(-100%); box-shadow: none; }
  .sidebar.open { transform: translateX(0); box-shadow: var(--shadow-lg); }
  .main-content, footer { margin-left: 0; }
  .mobile-menu-btn { display: flex; }
  .section { padding: 48px 24px; }
  .page-content { padding: 32px 24px; }
  .hero { padding: 60px 24px; }
  .friend-links-section { padding: 40px 24px; }
  .nav-links { display: none; }
  .hero-actions { flex-direction: column; align-items: center; }
}

/* ===== ACTIVE NAV (multi-page) ===== */
body#page-home .nav-home,
body#page-intro .nav-intro,
body#page-download .nav-download,
body#page-tutorial .nav-tutorial,
body#page-feed .nav-feed { color: var(--primary); background: var(--bg-secondary); font-weight: 600; }

body#page-home .sidebar-home,
body#page-intro .sidebar-intro,
body#page-download .sidebar-download,
body#page-tutorial .sidebar-tutorial,
body#page-feed .sidebar-feed { background: linear-gradient(135deg, rgba(59,130,246,0.12), rgba(6,182,212,0.08)); color: var(--primary); font-weight: 600; }
/* ===== COLLAPSIBLE SIDEBAR ===== */
.sidebar-toggle {
  width: 100%;
  background: none;
  border: none;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 10px 12px;
  border-radius: var(--radius-sm);
  font-size: 0.75rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 1px;
  color: var(--text-muted);
  font-family: var(--font-body);
  transition: all var(--transition);
  margin-bottom: 2px;
}
.sidebar-toggle:hover { color: var(--text); background: var(--bg-secondary); }
.sidebar-toggle.active { color: var(--primary); }
.sidebar-toggle-arrow { font-size: 0.6rem; transition: transform var(--transition); }
.sidebar-toggle-arrow.active { transform: rotate(0deg); }
.sidebar-section > .sidebar-links { padding-left: 4px; }