/* roulang page: index */
:root {
      --brand: #1A5FDC;
      --accent: #0EA5E9;
      --gold: #F59E0B;
      --surface: #F8FAFC;
      --deep: #0F172A;
      --muted: #475569;
      --soft: #94A3B8;
      --border-light: #E2E8F0;
    }

    * {
      box-sizing: border-box;
    }

    body {
      font-family: "PingFang SC", "Microsoft YaHei", "Helvetica Neue", sans-serif;
      background-color: var(--surface);
      color: var(--muted);
      line-height: 1.6;
      margin: 0;
      scroll-behavior: smooth;
    }

    img {
      max-width: 100%;
      height: auto;
      display: block;
    }

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

    /* 导航固定与阴影 */
    .navbar {
      position: fixed;
      top: 0;
      left: 0;
      width: 100%;
      height: 64px;
      background: white;
      z-index: 50;
      box-shadow: 0 1px 3px rgba(0,0,0,0.02);
      transition: box-shadow 0.2s ease;
    }
    .navbar.scrolled {
      box-shadow: 0 2px 8px rgba(0,0,0,0.08);
    }

    .nav-link {
      color: var(--muted);
      font-weight: 500;
      transition: color 0.2s;
      text-decoration: none;
      padding-bottom: 4px;
      border-bottom: 2px solid transparent;
    }
    .nav-link:hover,
    .nav-link.active {
      color: var(--brand);
      border-bottom-color: var(--brand);
    }

    /* 按钮系统 */
    .btn-primary {
      background-color: var(--gold);
      color: white;
      border-radius: 12px;
      padding: 16px 40px;
      font-weight: 600;
      font-size: 18px;
      border: none;
      cursor: pointer;
      display: inline-flex;
      align-items: center;
      justify-content: center;
      gap: 8px;
      transition: background 0.2s, transform 0.1s;
      text-decoration: none;
      box-shadow: 0 4px 10px rgba(245,158,11,0.25);
    }
    .btn-primary:hover {
      background-color: #D97706;
      transform: translateY(-1px);
      box-shadow: 0 8px 18px rgba(245,158,11,0.3);
    }

    .btn-outline {
      background: transparent;
      border: 2px solid var(--brand);
      color: var(--brand);
      border-radius: 12px;
      padding: 16px 40px;
      font-weight: 600;
      font-size: 18px;
      cursor: pointer;
      display: inline-flex;
      align-items: center;
      gap: 8px;
      transition: all 0.2s;
      text-decoration: none;
    }
    .btn-outline:hover {
      background-color: var(--brand);
      color: white;
    }

    .btn-download {
      background-color: var(--brand);
      color: white;
      border-radius: 12px;
      padding: 14px 32px;
      font-weight: 600;
      font-size: 16px;
      border: none;
      cursor: pointer;
      display: inline-flex;
      align-items: center;
      gap: 8px;
      transition: background 0.2s;
      text-decoration: none;
    }
    .btn-download:hover {
      background-color: var(--accent);
    }

    /* 卡片 */
    .card {
      background: white;
      border-radius: 16px;
      border: 1px solid var(--border-light);
      padding: 32px;
      box-shadow: 0 1px 3px rgba(0,0,0,0.04);
      transition: all 0.3s ease;
      height: 100%;
    }
    .card:hover {
      transform: translateY(-6px);
      box-shadow: 0 12px 28px rgba(0,0,0,0.08);
      border-color: var(--accent);
    }

    .stat-card {
      background: white;
      border-radius: 12px;
      padding: 24px 20px;
      text-align: center;
      border: 1px solid var(--border-light);
      transition: all 0.3s;
      box-shadow: 0 2px 6px rgba(0,0,0,0.02);
    }
    .stat-card:hover {
      border-color: var(--accent);
      box-shadow: 0 10px 20px rgba(0,0,0,0.06);
    }

    /* 手风琴 */
    .faq-item {
      border-bottom: 1px solid var(--border-light);
    }
    .faq-question {
      cursor: pointer;
      padding: 18px 0;
      display: flex;
      justify-content: space-between;
      align-items: center;
      font-weight: 600;
      color: var(--deep);
      font-size: 18px;
      transition: color 0.2s;
    }
    .faq-question:hover {
      color: var(--brand);
    }
    .faq-answer {
      max-height: 0;
      overflow: hidden;
      transition: max-height 0.35s ease, padding 0.2s;
      color: var(--muted);
      font-size: 16px;
      line-height: 1.7;
    }
    .faq-item.active .faq-answer {
      max-height: 200px;
      padding-bottom: 18px;
    }
    .faq-icon {
      transition: transform 0.3s;
    }
    .faq-item.active .faq-icon {
      transform: rotate(45deg);
    }

    /* 移动端菜单 */
    .mobile-menu {
      display: none;
      position: fixed;
      top: 64px;
      left: 0;
      width: 100%;
      height: calc(100vh - 64px);
      background: white;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      gap: 32px;
      z-index: 40;
    }
    .mobile-menu.open {
      display: flex;
    }
    .mobile-link {
      font-size: 22px;
      font-weight: 600;
      color: var(--deep);
    }

    @media (max-width: 768px) {
      .btn-primary, .btn-outline {
        padding: 14px 28px;
        font-size: 16px;
        width: 100%;
      }
      .card {
        padding: 24px;
      }
    }