/* 全局重置与设计系统 */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
:root {
  --brand-primary: #1a4b8c;
  --brand-secondary: #0b1a33;
  --brand-accent: #3b82f6;
  --brand-light: #e8f0fe;
  --glass-bg: rgba(255,255,255,0.65);
  --glass-border: rgba(255,255,255,0.25);
  --shadow-sm: 0 8px 20px rgba(0,0,0,0.04);
  --shadow-md: 0 20px 40px rgba(0,0,0,0.06);
  --shadow-xl: 0 30px 60px rgba(0,0,0,0.12);
  --radius-md: 20px;
  --radius-lg: 32px;
  --radius-xl: 40px;
  --transition: 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif;
  --bg-page: #f6f9fc;
  --text-primary: #0b1a33;
  --text-secondary: #2c3e50;
  --card-bg: #ffffff;
  --nav-bg: rgba(255,255,255,0.82);
}
body.dark {
  --bg-page: #0d1117;
  --text-primary: #e6edf3;
  --text-secondary: #b0c4de;
  --card-bg: #161b22;
  --nav-bg: rgba(13,17,23,0.88);
  --glass-bg: rgba(22,27,34,0.7);
  --glass-border: rgba(48,54,61,0.5);
  --shadow-sm: 0 8px 20px rgba(0,0,0,0.5);
  --shadow-md: 0 20px 40px rgba(0,0,0,0.6);
  --shadow-xl: 0 30px 60px rgba(0,0,0,0.7);
}
html { scroll-behavior: smooth; }
body {
  font-family: var(--font-sans);
  background: var(--bg-page);
  color: var(--text-primary);
  line-height: 1.6;
  transition: background 0.25s, color 0.25s;
}
a { color: var(--brand-accent); text-decoration: none; }
img, svg { display: block; max-width: 100%; height: auto; }
.container { max-width: 1280px; margin: 0 auto; padding: 0 28px; }

/* Header / 导航吸顶 */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: var(--nav-bg);
  backdrop-filter: blur(16px) saturate(180%);
  -webkit-backdrop-filter: blur(16px) saturate(180%);
  border-bottom: 1px solid var(--glass-border);
  box-shadow: var(--shadow-sm);
  transition: background 0.3s;
}
.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 12px 0;
  flex-wrap: wrap;
}
.logo svg { width: 140px; height: 44px; }
.nav-menu {
  display: flex;
  gap: 6px;
  list-style: none;
  flex-wrap: wrap;
}
.nav-menu li a {
  padding: 8px 18px;
  border-radius: 40px;
  font-weight: 500;
  font-size: 0.95rem;
  color: var(--text-primary);
  transition: var(--transition);
  background: transparent;
}
.nav-menu li a:hover, .nav-menu li a.active {
  background: var(--brand-accent);
  color: #fff;
  box-shadow: 0 4px 12px rgba(59,130,246,0.3);
}
.header-actions {
  display: flex;
  align-items: center;
  gap: 16px;
}
.dark-toggle {
  background: var(--card-bg);
  border: 1px solid var(--glass-border);
  border-radius: 40px;
  padding: 6px 14px;
  cursor: pointer;
  font-size: 1.2rem;
  box-shadow: var(--shadow-sm);
  transition: var(--transition);
  color: var(--text-primary);
}
.dark-toggle:hover { transform: scale(1.04); }
.mobile-menu-btn {
  display: none;
  background: transparent;
  border: none;
  font-size: 1.8rem;
  cursor: pointer;
  color: var(--text-primary);
}
@media (max-width: 768px) {
  .nav-menu { display: none; width: 100%; flex-direction: column; margin-top: 12px; background: var(--glass-bg); backdrop-filter: blur(12px); border-radius: var(--radius-md); padding: 12px; }
  .nav-menu.open { display: flex; }
  .mobile-menu-btn { display: inline-flex; }
}

/* 通用卡片/玻璃 */
.glass-card {
  background: var(--glass-bg);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border: 1px solid var(--glass-border);
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-sm);
  padding: 32px;
  transition: var(--transition);
}
.glass-card:hover { box-shadow: var(--shadow-md); transform: translateY(-4px); }
.card-shadow {
  background: var(--card-bg);
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-sm);
  padding: 28px;
  transition: var(--transition);
  border: 1px solid transparent;
}
.card-shadow:hover { box-shadow: var(--shadow-xl); border-color: var(--glass-border); }

/* 按钮 */
.btn-primary {
  display: inline-block;
  background: var(--brand-primary);
  color: #fff;
  padding: 14px 38px;
  border-radius: 60px;
  font-weight: 600;
  border: none;
  cursor: pointer;
  transition: var(--transition);
  box-shadow: 0 6px 14px rgba(26,75,140,0.25);
  font-size: 1rem;
}
.btn-primary:hover { background: #143b6e; transform: scale(1.02); box-shadow: 0 10px 20px rgba(26,75,140,0.35); }

/* Hero Banner 轮播 */
.hero-carousel {
  position: relative;
  border-radius: var(--radius-xl);
  overflow: hidden;
  margin: 28px 0 40px;
  min-height: 420px;
  background: linear-gradient(145deg, #0b1a33, #1a4b8c);
  box-shadow: var(--shadow-xl);
}
.hero-slide {
  display: none;
  padding: 60px 48px;
  color: #fff;
  animation: fadeSlide 0.8s ease;
}
.hero-slide.active { display: flex; flex-direction: column; justify-content: center; min-height: 420px; }
@keyframes fadeSlide { 0% { opacity: 0; transform: translateY(12px); } 100% { opacity: 1; transform: translateY(0); } }
.hero-slide h1 { font-size: 3.2rem; font-weight: 700; line-height: 1.2; max-width: 720px; margin-bottom: 24px; }
.hero-slide p { font-size: 1.2rem; max-width: 620px; opacity: 0.9; margin-bottom: 32px; }
.hero-indicators { position: absolute; bottom: 24px; left: 50%; transform: translateX(-50%); display: flex; gap: 12px; }
.hero-indicators span { width: 12px; height: 12px; border-radius: 20px; background: rgba(255,255,255,0.3); cursor: pointer; transition: var(--transition); }
.hero-indicators span.active { background: #fff; width: 32px; }

/* 通用section */
section { padding: 48px 0; }
.section-title { font-size: 2.2rem; font-weight: 600; margin-bottom: 24px; letter-spacing: -0.02em; }
.grid-2 { display: grid; grid-template-columns: 1fr 1fr; gap: 32px; }
.grid-3 { display: grid; grid-template-columns: repeat(3, 1fr); gap: 28px; }
.grid-4 { display: grid; grid-template-columns: repeat(4, 1fr); gap: 24px; }
@media (max-width: 900px) { .grid-2, .grid-3, .grid-4 { grid-template-columns: 1fr; } }

/* 数字动画 */
.stat-number { font-size: 2.8rem; font-weight: 700; color: var(--brand-primary); }

/* Footer */
.site-footer {
  background: var(--brand-secondary);
  color: #cbd5e1;
  padding: 48px 0 24px;
  margin-top: 40px;
  border-radius: var(--radius-xl) var(--radius-xl) 0 0;
}
.footer-grid { display: grid; grid-template-columns: 2fr 1fr 1fr 1fr; gap: 32px; }
@media (max-width: 768px) { .footer-grid { grid-template-columns: 1fr 1fr; } }
.site-footer a { color: #94a3b8; }
.site-footer a:hover { color: #fff; }

/* FAQ折叠 */
.faq-item { border-bottom: 1px solid var(--glass-border); padding: 18px 0; }
.faq-question { font-weight: 600; cursor: pointer; display: flex; justify-content: space-between; align-items: center; font-size: 1.1rem; }
.faq-answer { max-height: 0; overflow: hidden; transition: max-height 0.4s ease, padding 0.2s; padding-top: 0; color: var(--text-secondary); }
.faq-item.open .faq-answer { max-height: 260px; padding-top: 14px; }

/* 滚动动画 */
.fade-up { opacity: 0; transform: translateY(30px); transition: opacity 0.7s ease, transform 0.7s ease; }
.fade-up.visible { opacity: 1; transform: translateY(0); }

/* 返回顶部 */
.back-to-top {
  position: fixed;
  bottom: 30px; right: 30px;
  background: var(--brand-primary);
  color: #fff;
  width: 48px; height: 48px;
  border-radius: 60px;
  display: flex; align-items: center; justify-content: center;
  font-size: 1.6rem;
  box-shadow: var(--shadow-md);
  cursor: pointer;
  opacity: 0; visibility: hidden;
  transition: var(--transition);
  border: none;
  z-index: 99;
}
.back-to-top.show { opacity: 1; visibility: visible; }
.back-to-top:hover { transform: scale(1.06); background: #143b6e; }

/* 搜索模拟 */
.search-sim {
  display: flex;
  background: var(--card-bg);
  border-radius: 60px;
  padding: 4px 4px 4px 20px;
  border: 1px solid var(--glass-border);
  max-width: 400px;
}
.search-sim input { border: none; background: transparent; flex:1; padding: 12px 0; outline: none; font-size: 1rem; color: var(--text-primary); }
.search-sim button { background: var(--brand-accent); color: #fff; border: none; border-radius: 40px; padding: 10px 28px; font-weight: 500; cursor: pointer; }
@media (max-width: 600px) { .hero-slide h1 { font-size: 2rem; } .hero-slide { padding: 32px 20px; } }