/* 全局重置与基础样式 */
*, *::before, *::after { margin: 0; padding: 0; box-sizing: border-box; }
html { scroll-behavior: smooth; }
body { font-family: 'Segoe UI', Roboto, 'Helvetica Neue', sans-serif; background: #f8f9fc; color: #1a1a2e; line-height: 1.6; transition: background 0.3s, color 0.3s; }
img, svg { display: block; max-width: 100%; height: auto; }
a { text-decoration: none; color: inherit; }
ul { list-style: none; }
.container { max-width: 1200px; margin: 0 auto; padding: 0 20px; }
/* 渐变背景与品牌色 */
.gradient-bg { background: linear-gradient(135deg, #1a73e8 0%, #0d47a1 100%); }
.card { background: rgba(255,255,255,0.8); backdrop-filter: blur(12px); -webkit-backdrop-filter: blur(12px); border-radius: 20px; box-shadow: 0 8px 32px rgba(0,0,0,0.06); padding: 30px; transition: transform 0.3s, box-shadow 0.3s; }
.card:hover { transform: translateY(-5px); box-shadow: 0 16px 48px rgba(0,0,0,0.1); }
.btn { display: inline-block; padding: 12px 30px; border-radius: 50px; font-weight: 600; transition: all 0.3s; cursor: pointer; border: none; }
.btn-primary { background: #1a73e8; color: #fff; }
.btn-primary:hover { background: #1557b0; transform: translateY(-2px); box-shadow: 0 8px 20px rgba(26,115,232,0.3); }
.section-title { font-size: 2.2rem; font-weight: 700; margin-bottom: 15px; color: #1a1a2e; }
.section-subtitle { font-size: 1.1rem; color: #5f6368; margin-bottom: 40px; }
/* 暗黑模式 */
body.dark-mode { background: #121212; color: #e0e0e0; }
body.dark-mode .card { background: rgba(30,30,40,0.8); backdrop-filter: blur(12px); }
body.dark-mode .section-title { color: #e0e0e0; }
body.dark-mode .section-subtitle { color: #aaa; }
body.dark-mode .gradient-bg { background: linear-gradient(135deg, #0d47a1 0%, #1a237e 100%); }
/* 响应式 */
@media (max-width: 768px) {
    .section-title { font-size: 1.8rem; }
    .container { padding: 0 15px; }
}
/* 导航 */
.navbar { position: fixed; top: 0; left: 0; right: 0; z-index: 1000; background: rgba(255,255,255,0.85); backdrop-filter: blur(16px); -webkit-backdrop-filter: blur(16px); border-bottom: 1px solid rgba(0,0,0,0.05); padding: 0 20px; transition: background 0.3s; }
body.dark-mode .navbar { background: rgba(18,18,18,0.85); border-bottom-color: rgba(255,255,255,0.05); }
.navbar .container { display: flex; align-items: center; justify-content: space-between; height: 70px; }
.navbar .logo { font-size: 1.8rem; font-weight: 800; color: #1a73e8; }
body.dark-mode .navbar .logo { color: #64b5f6; }
.nav-links { display: flex; gap: 25px; align-items: center; }
.nav-links a { font-weight: 500; font-size: 0.95rem; padding: 8px 0; position: relative; transition: color 0.3s; }
.nav-links a::after { content: ''; position: absolute; bottom: 0; left: 0; width: 0; height: 2px; background: #1a73e8; transition: width 0.3s; }
.nav-links a:hover::after, .nav-links a.active::after { width: 100%; }
body.dark-mode .nav-links a { color: #e0e0e0; }
.hamburger { display: none; flex-direction: column; gap: 5px; cursor: pointer; }
.hamburger span { width: 28px; height: 3px; background: #1a1a2e; border-radius: 5px; transition: all 0.3s; }
body.dark-mode .hamburger span { background: #e0e0e0; }
.mobile-menu { display: none; position: fixed; top: 70px; left: 0; right: 0; background: rgba(255,255,255,0.98); backdrop-filter: blur(16px); padding: 20px; box-shadow: 0 10px 30px rgba(0,0,0,0.1); z-index: 999; }
body.dark-mode .mobile-menu { background: rgba(18,18,18,0.98); }
.mobile-menu a { display: block; padding: 12px 0; font-weight: 500; border-bottom: 1px solid rgba(0,0,0,0.05); }
@media (max-width: 768px) {
    .nav-links { display: none; }
    .hamburger { display: flex; }
    .mobile-menu.open { display: block; }
}
/* Hero Banner */
.hero { padding-top: 100px; padding-bottom: 60px; background: linear-gradient(135deg, #e8f0fe 0%, #d2e3fc 100%); min-height: 80vh; display: flex; align-items: center; position: relative; overflow: hidden; }
body.dark-mode .hero { background: linear-gradient(135deg, #1a1a2e 0%, #16213e 100%); }
.hero .container { display: flex; align-items: center; justify-content: space-between; flex-wrap: wrap; }
.hero-content { flex: 1; min-width: 300px; }
.hero-content h1 { font-size: 3.2rem; font-weight: 800; line-height: 1.2; margin-bottom: 20px; color: #0d47a1; }
body.dark-mode .hero-content h1 { color: #64b5f6; }
.hero-content p { font-size: 1.2rem; color: #3c4043; margin-bottom: 30px; max-width: 500px; }
body.dark-mode .hero-content p { color: #b0b0b0; }
.hero-image { flex: 1; min-width: 300px; text-align: center; }
.hero-image svg { max-width: 100%; height: auto; }
.banner-indicators { position: absolute; bottom: 30px; left: 50%; transform: translateX(-50%); display: flex; gap: 10px; }
.banner-indicators span { width: 12px; height: 12px; border-radius: 50%; background: rgba(26,115,232,0.3); cursor: pointer; transition: background 0.3s; }
.banner-indicators span.active { background: #1a73e8; }
@media (max-width: 768px) {
    .hero-content h1 { font-size: 2.2rem; }
}
/* 通用模块间距 */
section { padding: 80px 0; }
/* 网格布局 */
.grid-2 { display: grid; grid-template-columns: repeat(2, 1fr); gap: 30px; }
.grid-3 { display: grid; grid-template-columns: repeat(3, 1fr); gap: 30px; }
.grid-4 { display: grid; grid-template-columns: repeat(4, 1fr); gap: 25px; }
@media (max-width: 768px) {
    .grid-2, .grid-3, .grid-4 { grid-template-columns: 1fr; }
}
.text-center { text-align: center; }
.mt-20 { margin-top: 20px; }
.mb-20 { margin-bottom: 20px; }
/* 数据展示 */
.stats-grid { display: flex; justify-content: center; gap: 50px; flex-wrap: wrap; }
.stat-item { text-align: center; }
.stat-number { font-size: 2.8rem; font-weight: 800; color: #1a73e8; }
body.dark-mode .stat-number { color: #64b5f6; }
.stat-label { color: #5f6368; font-size: 1rem; }
/* FAQ */
.faq-item { border-bottom: 1px solid #e0e0e0; padding: 15px 0; }
body.dark-mode .faq-item { border-color: #333; }
.faq-question { display: flex; justify-content: space-between; align-items: center; cursor: pointer; font-weight: 600; font-size: 1.1rem; }
.faq-question span { transition: transform 0.3s; }
.faq-answer { max-height: 0; overflow: hidden; transition: max-height 0.4s ease; padding-top: 0; color: #5f6368; }
body.dark-mode .faq-answer { color: #aaa; }
.faq-item.open .faq-answer { max-height: 200px; padding-top: 15px; }
.faq-item.open .faq-question span { transform: rotate(180deg); }
/* Footer */
footer { background: #0d47a1; color: #fff; padding: 60px 0 30px; }
body.dark-mode footer { background: #0a0a1a; }
footer a { color: #bbdefb; transition: color 0.3s; }
footer a:hover { color: #fff; }
.footer-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: 30px; }
@media (max-width: 768px) { .footer-grid { grid-template-columns: 1fr 1fr; } }
@media (max-width: 480px) { .footer-grid { grid-template-columns: 1fr; } }
footer h4 { margin-bottom: 20px; font-size: 1.2rem; }
footer ul li { margin-bottom: 10px; }
.copyright { text-align: center; padding-top: 30px; border-top: 1px solid rgba(255,255,255,0.1); margin-top: 30px; }
/* 回到顶部 */
.back-to-top { position: fixed; bottom: 30px; right: 30px; width: 50px; height: 50px; background: #1a73e8; color: #fff; border: none; border-radius: 50%; font-size: 1.5rem; cursor: pointer; display: none; align-items: center; justify-content: center; box-shadow: 0 4px 15px rgba(0,0,0,0.2); z-index: 999; transition: opacity 0.3s; }
body.dark-mode .back-to-top { background: #64b5f6; color: #121212; }
.back-to-top.show { display: flex; }
/* 搜索 */
.search-box { display: flex; gap: 10px; max-width: 500px; margin: 20px auto; }
.search-box input { flex: 1; padding: 12px 20px; border-radius: 50px; border: 2px solid #e0e0e0; font-size: 1rem; outline: none; transition: border 0.3s; }
.search-box input:focus { border-color: #1a73e8; }
body.dark-mode .search-box input { background: #2a2a3a; border-color: #444; color: #e0e0e0; }
.search-box button { padding: 12px 25px; border-radius: 50px; border: none; background: #1a73e8; color: #fff; font-weight: 600; cursor: pointer; transition: background 0.3s; }
.search-box button:hover { background: #1557b0; }
/* 懒加载图片容器 */
.lazy-img { opacity: 0; transition: opacity 0.5s; }
.lazy-img.loaded { opacity: 1; }
/* 滚动动画 */
.fade-up { opacity: 0; transform: translateY(30px); transition: opacity 0.6s ease, transform 0.6s ease; }
.fade-up.visible { opacity: 1; transform: translateY(0); }