/* roulang page: index */
/* 设计变量与全局重置 */
    :root {
      --primary: #1A5F7A;
      --primary-hover: #145069;
      --accent: #E85D04;
      --accent-hover: #C94D03;
      --bg: #F7F9FC;
      --card-bg: #FFFFFF;
      --text-dark: #1E293B;
      --text-mid: #64748B;
      --text-light: #94A3B8;
      --border: #E2E8F0;
      --trust: #10B981;
      --radius-lg: 12px;
      --radius-md: 8px;
      --shadow-sm: 0 1px 3px rgba(0,0,0,0.06), 0 1px 2px rgba(0,0,0,0.04);
      --shadow-hover: 0 10px 25px rgba(0,0,0,0.08), 0 4px 10px rgba(0,0,0,0.04);
      --font-stack: "PingFang SC", "Microsoft YaHei", "Helvetica Neue", Arial, sans-serif;
      --transition: 0.3s ease;
    }
    * {
      box-sizing: border-box;
    }
    html {
      scroll-behavior: smooth;
      scroll-padding-top: 80px;
    }
    body {
      margin: 0;
      font-family: var(--font-stack);
      background-color: var(--bg);
      color: var(--text-dark);
      line-height: 1.6;
      -webkit-font-smoothing: antialiased;
    }
    img {
      max-width: 100%;
      display: block;
      object-fit: cover;
    }
    a {
      text-decoration: none;
      color: inherit;
    }
    button, input, textarea {
      font-family: inherit;
    }
    .container {
      max-width: 1200px;
      margin-left: auto;
      margin-right: auto;
      padding-left: 24px;
      padding-right: 24px;
    }
    /* 导航固定头 */
    #header {
      position: fixed;
      top: 0;
      left: 0;
      width: 100%;
      background: white;
      z-index: 50;
      height: 72px;
      display: flex;
      align-items: center;
      transition: height 0.3s, box-shadow 0.3s;
      box-shadow: 0 2px 8px rgba(0,0,0,0.04);
    }
    .header-inner {
      display: flex;
      justify-content: space-between;
      align-items: center;
      width: 100%;
    }
    .logo {
      display: flex;
      align-items: center;
      gap: 8px;
      font-weight: 700;
      font-size: 1.5rem;
      color: var(--primary);
    }
    .logo i {
      color: var(--accent);
    }
    .nav-menu {
      display: flex;
      gap: 32px;
      align-items: center;
    }
    .nav-link {
      font-weight: 500;
      font-size: 1rem;
      color: var(--text-dark);
      position: relative;
      padding: 8px 0;
      transition: color 0.2s;
    }
    .nav-link:hover, .nav-link.active {
      color: var(--primary);
    }
    .nav-link.active::after {
      content: '';
      position: absolute;
      bottom: 0;
      left: 0;
      width: 100%;
      height: 2px;
      background: var(--primary);
    }
    .btn-primary {
      background: var(--accent);
      color: white;
      padding: 12px 28px;
      border-radius: var(--radius-md);
      font-weight: 600;
      display: inline-block;
      transition: background 0.2s, transform 0.2s;
      border: none;
      cursor: pointer;
    }
    .btn-primary:hover {
      background: var(--accent-hover);
      transform: translateY(-2px);
    }
    .btn-outline {
      background: transparent;
      border: 2px solid var(--primary);
      color: var(--primary);
      padding: 12px 28px;
      border-radius: var(--radius-md);
      font-weight: 600;
      display: inline-block;
      transition: all 0.2s;
    }
    .btn-outline:hover {
      background: var(--primary);
      color: white;
    }
    /* 移动端汉堡菜单 */
    #menu-toggle {
      display: none;
      background: none;
      border: none;
      font-size: 2rem;
      color: var(--primary);
    }
    .mobile-menu {
      display: none;
      position: fixed;
      top: 72px;
      left: 0;
      width: 100%;
      background: white;
      flex-direction: column;
      padding: 24px;
      box-shadow: 0 10px 20px rgba(0,0,0,0.05);
      z-index: 40;
    }
    .mobile-menu a {
      padding: 16px 0;
      border-bottom: 1px solid var(--border);
      font-weight: 500;
    }
    /* 板块通用间距 */
    section {
      padding: 100px 0;
    }
    @media (max-width: 768px) {
      section {
        padding: 70px 0;
      }
    }
    /* 卡片系统 */
    .card {
      background: var(--card-bg);
      border-radius: var(--radius-lg);
      box-shadow: var(--shadow-sm);
      transition: var(--transition);
      overflow: hidden;
    }
    .card:hover {
      transform: translateY(-6px);
      box-shadow: var(--shadow-hover);
    }
    .feature-icon {
      width: 56px;
      height: 56px;
      color: var(--primary);
    }
    /* 数据数字动画 */
    .stat-number {
      font-size: 3rem;
      font-weight: 700;
      color: var(--primary);
      line-height: 1.2;
    }
    /* 手风琴 */
    .faq-item {
      border-bottom: 1px solid var(--border);
      background: white;
      border-radius: var(--radius-md);
      margin-bottom: 12px;
      overflow: hidden;
    }
    .faq-question {
      width: 100%;
      background: none;
      border: none;
      padding: 20px 24px;
      text-align: left;
      font-weight: 600;
      font-size: 1.1rem;
      display: flex;
      justify-content: space-between;
      align-items: center;
      cursor: pointer;
      color: var(--text-dark);
    }
    .faq-answer {
      padding: 0 24px 20px;
      color: var(--text-mid);
      display: none;
      line-height: 1.7;
    }
    .faq-item.active .faq-answer {
      display: block;
    }
    .faq-item.active .faq-icon {
      transform: rotate(45deg);
    }
    /* CTA 深色背景 */
    .bg-primary-dark {
      background-color: var(--primary);
    }
    /* 页脚 */
    footer {
      background: #1E293B;
      color: #CBD5E1;
      padding: 60px 0 30px;
    }