/* 全局重置与基础 */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  font-family: system-ui, -apple-system, 'Segoe UI', Roboto, sans-serif;
  background: #f6f9fc;
  color: #1a2332;
  transition: background 0.3s, color 0.3s;
  line-height: 1.6;
}

body.dark {
  background: #0b1421;
  color: #e6edf5;
}

a {
  color: inherit;
  text-decoration: none;
}

.container {
  max-width: 1280px;
  margin: 0 auto;
  padding: 0 20px;
}

/* 玻璃效果 & 阴影 */
.glass {
  background: rgba(255, 255, 255, 0.7);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-radius: 24px;
  box-shadow: 0 15px 35px -10px rgba(0, 0, 0, 0.08);
}

body.dark .glass {
  background: rgba(20, 30, 50, 0.6);
  box-shadow: 0 15px 35px -10px rgba(0, 0, 0, 0.5);
}

.card {
  background: #ffffff;
  border-radius: 28px;
  padding: 24px;
  box-shadow: 0 10px 25px -8px rgba(0, 0, 0, 0.05);
  transition: transform 0.2s, box-shadow 0.3s;
}

body.dark .card {
  background: #1c2a3f;
}

.card:hover {
  transform: translateY(-4px);
  box-shadow: 0 20px 35px -12px rgba(0, 20, 40, 0.2);
}

.btn {
  display: inline-block;
  background: #1e3a5f;
  color: #fff;
  border-radius: 60px;
  padding: 12px 28px;
  font-weight: 600;
  border: none;
  cursor: pointer;
  transition: background 0.2s;
}

.btn:hover {
  background: #14314f;
}

body.dark .btn {
  background: #2d4b74;
}

.section-title {
  font-size: 2rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  margin-bottom: 24px;
}

.grid-2 {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 28px;
}

.grid-3 {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 24px;
}

.grid-4 {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 20px;
}

.flex-center {
  display: flex;
  align-items: center;
  justify-content: center;
}

/* 头部 */
header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(255, 255, 255, 0.75);
  backdrop-filter: blur(18px);
  border-bottom: 1px solid rgba(0, 0, 0, 0.02);
}

body.dark header {
  background: rgba(11, 20, 33, 0.8);
  border-bottom: 1px solid #2a3a50;
}

.header-inner {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 14px 0;
  flex-wrap: wrap;
}

.logo svg {
  height: 40px;
  width: auto;
  display: block;
}

.nav {
  display: flex;
  gap: 20px;
}

.nav a {
  font-weight: 500;
  padding: 6px 0;
  border-bottom: 2px solid transparent;
  transition: 0.2s;
}

.nav a.active,
.nav a:hover {
  border-bottom-color: #1e3a5f;
  color: #1e3a5f;
}

body.dark .nav a.active,
body.dark .nav a:hover {
  border-bottom-color: #6d8cb0;
  color: #b6d0e8;
}

.hamburger {
  display: none;
  flex-direction: column;
  gap: 5px;
  cursor: pointer;
  background: none;
  border: none;
}

.hamburger span {
  width: 28px;
  height: 2px;
  background: #1a2332;
  border-radius: 4px;
}

body.dark .hamburger span {
  background: #e6edf5;
}

.dark-toggle {
  background: none;
  border: 1px solid #b0c8dd;
  border-radius: 40px;
  padding: 6px 16px;
  font-size: 0.9rem;
  cursor: pointer;
}

/* 移动菜单 */
.mobile-nav {
  display: none;
  flex-direction: column;
  gap: 12px;
  padding: 20px 0;
}

.mobile-nav.open {
  display: flex;
}

/* banner 轮播 */
.hero {
  border-radius: 32px;
  overflow: hidden;
  position: relative;
  margin: 30px 0;
  background: linear-gradient(145deg, #0b1f33, #1a3a5c);
  min-height: 400px;
  display: flex;
  align-items: center;
}

body.dark .hero {
  background: linear-gradient(145deg, #0a1628, #1b2e4a);
}

.hero-slide {
  padding: 50px 40px;
  width: 100%;
}

.hero h1 {
  font-size: 3.2rem;
  font-weight: 700;
  color: #fff;
  line-height: 1.2;
  max-width: 600px;
}

.hero p {
  color: rgba(255, 255, 255, 0.8);
  font-size: 1.2rem;
  margin: 20px 0 30px;
  max-width: 550px;
}

.hero .btn {
  background: #ffb347;
  color: #0b1a2e;
}

.hero-indicators {
  display: flex;
  gap: 10px;
  position: absolute;
  bottom: 20px;
  left: 40px;
}

.hero-indicators span {
  width: 40px;
  height: 4px;
  background: rgba(255, 255, 255, 0.3);
  border-radius: 10px;
  cursor: pointer;
}

.hero-indicators span.active {
  background: #ffb347;
}

/* 数字动画 */
.stat-number {
  font-size: 2.6rem;
  font-weight: 700;
  color: #1e3a5f;
}

body.dark .stat-number {
  color: #9bb9da;
}

/* FAQ折叠 */
.faq-item {
  border-bottom: 1px solid #dbe3ed;
  padding: 18px 0;
}

body.dark .faq-item {
  border-color: #2a3a4f;
}

.faq-question {
  font-weight: 600;
  cursor: pointer;
  display: flex;
  justify-content: space-between;
}

.faq-answer {
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.4s ease;
  opacity: 0.8;
}

.faq-item.open .faq-answer {
  max-height: 300px;
  margin-top: 12px;
}

.footer {
  margin-top: 60px;
  border-top: 1px solid #dce3ed;
  padding: 40px 0 20px;
}

body.dark .footer {
  border-color: #2a3a50;
}

.footer-grid {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr 1fr;
  gap: 30px;
}

/* 响应式 */
@media (max-width: 1024px) {
  .grid-4 {
    grid-template-columns: repeat(2, 1fr);
  }
  .footer-grid {
    grid-template-columns: 1fr 1fr;
  }
}

@media (max-width: 768px) {
  .nav {
    display: none;
  }
  .hamburger {
    display: flex;
  }
  .grid-2,
  .grid-3,
  .grid-4 {
    grid-template-columns: 1fr;
  }
  .hero h1 {
    font-size: 2.2rem;
  }
  .footer-grid {
    grid-template-columns: 1fr;
  }
  .header-inner {
    flex-wrap: wrap;
  }
}

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

.fade-up.show {
  opacity: 1;
  transform: translateY(0);
}

/* 其他 */
.badge {
  background: #eaf1fa;
  border-radius: 60px;
  padding: 4px 16px;
  font-size: 0.85rem;
}

body.dark .badge {
  background: #26354c;
}

.back-to-top {
  position: fixed;
  bottom: 30px;
  right: 30px;
  background: #1e3a5f;
  color: #fff;
  border: none;
  border-radius: 60px;
  padding: 12px 18px;
  cursor: pointer;
  opacity: 0;
  transition: opacity 0.3s;
  z-index: 99;
}

.back-to-top.visible {
  opacity: 0.8;
}

img[loading="lazy"] {
  background: #eef3f9;
}