/* roulang page: index */
:root {
      --color-brand: #1A5F7A;
      --color-brand-hover: #15536B;
      --color-accent: #0D9488;
      --color-accent-hover: #0F766E;
      --color-bg: #FAFBFD;
      --color-card: #FFFFFF;
      --color-text-heading: #0F172A;
      --color-text-body: #334155;
      --color-text-muted: #64748B;
      --color-border: #E2E8F0;
      --color-footer-bg: #0F172A;
      --radius-card: 16px;
      --radius-button: 12px;
      --shadow-sm: 0 1px 2px 0 rgba(0,0,0,0.03);
      --shadow-md: 0 4px 12px rgba(0,0,0,0.05);
      --shadow-lg: 0 12px 28px rgba(0,0,0,0.08);
      --transition: all 0.3s ease;
    }

    * {
      margin: 0;
      padding: 0;
      box-sizing: border-box;
    }

    body {
      font-family: 'Inter', 'PingFang SC', 'Microsoft YaHei', system-ui, sans-serif;
      background-color: var(--color-bg);
      color: var(--color-text-body);
      line-height: 1.75;
      -webkit-font-smoothing: antialiased;
      scroll-behavior: smooth;
    }

    .container {
      max-width: 1280px;
      margin-left: auto;
      margin-right: auto;
      padding-left: 1.5rem;
      padding-right: 1.5rem;
    }

    /* 按钮基础 */
    .btn {
      display: inline-flex;
      align-items: center;
      justify-content: center;
      font-weight: 600;
      border-radius: var(--radius-button);
      padding: 0.7rem 1.8rem;
      font-size: 1rem;
      transition: var(--transition);
      cursor: pointer;
      text-decoration: none;
      line-height: 1.2;
      border: 2px solid transparent;
    }

    .btn-primary {
      background-color: var(--color-brand);
      color: white;
    }
    .btn-primary:hover {
      background-color: var(--color-brand-hover);
      transform: translateY(-1px);
      box-shadow: 0 8px 18px rgba(26,95,122,0.25);
    }

    .btn-outline {
      background: transparent;
      border-color: var(--color-brand);
      color: var(--color-brand);
    }
    .btn-outline:hover {
      background-color: var(--color-brand);
      color: white;
      transform: translateY(-1px);
    }

    .card {
      background: var(--color-card);
      border-radius: var(--radius-card);
      box-shadow: var(--shadow-md);
      padding: 2rem;
      transition: var(--transition);
      height: 100%;
      display: flex;
      flex-direction: column;
    }
    .card:hover {
      box-shadow: var(--shadow-lg);
      transform: translateY(-5px);
    }

    .section-title {
      font-size: 2rem;
      font-weight: 700;
      color: var(--color-text-heading);
      margin-bottom: 0.75rem;
    }
    .section-subtitle {
      color: var(--color-text-muted);
      font-size: 1.1rem;
      margin-bottom: 3rem;
    }

    /* 导航样式 */
    .nav-link {
      font-weight: 500;
      color: var(--color-text-body);
      text-decoration: none;
      padding: 0.4rem 0.2rem;
      border-bottom: 2px solid transparent;
      transition: var(--transition);
      white-space: nowrap;
    }
    .nav-link:hover {
      color: var(--color-accent);
    }
    .nav-link.active {
      color: var(--color-brand);
      border-bottom-color: var(--color-brand);
      font-weight: 600;
    }

    /* FAQ折叠 */
    .faq-item {
      border-bottom: 1px solid var(--color-border);
      padding: 1.2rem 0;
    }
    .faq-question {
      font-weight: 600;
      color: var(--color-text-heading);
      cursor: pointer;
      display: flex;
      justify-content: space-between;
      align-items: center;
      font-size: 1.1rem;
    }
    .faq-icon {
      font-size: 1.8rem;
      font-weight: 300;
      color: var(--color-brand);
      transition: transform 0.2s;
    }
    .faq-answer {
      max-height: 0;
      overflow: hidden;
      transition: max-height 0.35s ease;
      color: var(--color-text-body);
      padding-right: 2rem;
    }
    .faq-item.open .faq-answer {
      max-height: 300px;
      margin-top: 0.8rem;
    }
    .faq-item.open .faq-icon {
      transform: rotate(45deg);
    }

    /* 移动菜单 */
    .mobile-menu {
      display: none;
      flex-direction: column;
      background: white;
      position: absolute;
      top: 100%;
      left: 0;
      width: 100%;
      box-shadow: var(--shadow-lg);
      padding: 1.5rem;
      gap: 1.2rem;
      border-top: 1px solid var(--color-border);
    }
    .mobile-menu.active {
      display: flex;
    }

    @media (max-width: 768px) {
      .section-title {
        font-size: 1.8rem;
      }
      .card {
        padding: 1.5rem;
      }
    }