/* roulang page: index */
/* ===== 设计变量与基础重置 ===== */
    :root {
      --primary: #0A4C7B;
      --primary-dark: #0A2E4A;
      --accent: #F85C3C;
      --accent-hover: #e64a2e;
      --bg-light: #F4F8FC;
      --bg-dark: #0A2E4A;
      --text-dark: #1A1A1A;
      --text-body: #4A4A4A;
      --text-muted: #7A7A7A;
      --white: #FFFFFF;
      --border-light: #E2E8F0;
      --shadow-card: 0 4px 20px rgba(10, 44, 74, 0.08);
      --shadow-hover: 0 8px 30px rgba(10, 44, 74, 0.15);
      --radius-card: 12px;
      --radius-btn: 8px;
      --radius-img: 16px;
      --transition: 0.3s ease;
      --font-sans: 'PingFang SC', 'Microsoft YaHei', 'Noto Sans SC', 'Inter', 'SF Pro Text', sans-serif;
      --container-max: 1200px;
    }

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

    html {
      scroll-behavior: smooth;
      font-size: 16px;
    }

    body {
      font-family: var(--font-sans);
      background-color: var(--white);
      color: var(--text-body);
      line-height: 1.75;
      -webkit-font-smoothing: antialiased;
      overflow-x: hidden;
    }

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

    a {
      text-decoration: none;
      color: inherit;
      transition: color var(--transition);
    }

    button, .btn {
      cursor: pointer;
      font-family: inherit;
      border: none;
      background: none;
      transition: all var(--transition);
      display: inline-flex;
      align-items: center;
      justify-content: center;
      gap: 8px;
    }

    .container {
      max-width: var(--container-max);
      margin: 0 auto;
      padding: 0 24px;
    }

    /* 通用标题样式 */
    h1, h2, h3, h4 {
      font-weight: 700;
      line-height: 1.3;
    }

    h2 {
      font-size: 2.25rem;
      color: var(--primary);
      margin-bottom: 1rem;
    }

    @media (max-width: 768px) {
      h2 {
        font-size: 1.75rem;
      }
    }

    /* 卡片系统 */
    .card {
      background: var(--white);
      border-radius: var(--radius-card);
      box-shadow: var(--shadow-card);
      transition: all var(--transition);
      overflow: hidden;
    }

    .card:hover {
      box-shadow: var(--shadow-hover);
      transform: translateY(-4px);
    }

    /* 按钮系统 */
    .btn-primary {
      background-color: var(--primary);
      color: var(--white);
      padding: 14px 32px;
      border-radius: var(--radius-btn);
      font-weight: 600;
      font-size: 1rem;
    }

    .btn-primary:hover {
      background-color: var(--accent);
      box-shadow: 0 4px 12px rgba(248, 92, 60, 0.35);
    }

    .btn-outline {
      border: 2px solid var(--primary);
      color: var(--primary);
      padding: 12px 30px;
      border-radius: var(--radius-btn);
      font-weight: 600;
      background: transparent;
    }

    .btn-outline:hover {
      background-color: var(--primary);
      color: var(--white);
    }

    .btn-large {
      padding: 16px 40px;
      font-size: 1.1rem;
    }

    .btn-accent-large {
      background-color: var(--accent);
      color: var(--white);
      padding: 16px 48px;
      border-radius: 50px;
      font-weight: 700;
      font-size: 1.2rem;
      box-shadow: 0 8px 20px rgba(248, 92, 60, 0.3);
    }

    .btn-accent-large:hover {
      background-color: #ff7a5c;
      transform: translateY(-2px);
      box-shadow: 0 12px 24px rgba(248, 92, 60, 0.4);
    }

    /* 区块间距 */
    section {
      padding: 100px 0;
    }

    @media (max-width: 768px) {
      section {
        padding: 60px 0;
      }
    }

    /* 导航样式 */
    .main-header {
      position: fixed;
      top: 0;
      left: 0;
      width: 100%;
      background: rgba(255,255,255,0.96);
      backdrop-filter: blur(8px);
      box-shadow: 0 2px 12px rgba(0,0,0,0.04);
      z-index: 1000;
      height: 72px;
      display: flex;
      align-items: center;
    }

    .nav-container {
      display: flex;
      justify-content: space-between;
      align-items: center;
      width: 100%;
    }

    .logo {
      display: flex;
      align-items: center;
      gap: 10px;
      font-weight: 700;
      font-size: 1.5rem;
      color: var(--primary-dark);
    }

    .logo i {
      font-size: 2rem;
      color: var(--accent);
    }

    .nav-links {
      display: flex;
      gap: 2rem;
      align-items: center;
      list-style: none;
    }

    .nav-links a {
      font-weight: 500;
      color: var(--text-body);
      padding: 8px 0;
      border-bottom: 3px solid transparent;
      transition: all var(--transition);
    }

    .nav-links a:hover,
    .nav-links a.active {
      color: var(--primary);
      border-bottom-color: var(--primary);
    }

    .hamburger {
      display: none;
      font-size: 1.8rem;
      cursor: pointer;
      color: var(--primary-dark);
    }

    @media (max-width: 768px) {
      .nav-links {
        position: fixed;
        top: 72px;
        left: 0;
        width: 100%;
        background: white;
        flex-direction: column;
        padding: 2rem;
        gap: 1.5rem;
        box-shadow: 0 10px 20px rgba(0,0,0,0.05);
        transform: translateY(-150%);
        transition: transform 0.4s ease;
        z-index: 999;
      }
      .nav-links.active {
        transform: translateY(0);
      }
      .hamburger {
        display: block;
      }
    }

    /* 背景区域 */
    .bg-light-section {
      background-color: var(--bg-light);
    }

    .bg-dark-section {
      background-color: var(--bg-dark);
    }

    /* 特殊网格 */
    .feature-grid {
      display: grid;
      grid-template-columns: repeat(3, 1fr);
      gap: 24px;
    }

    .feature-grid .feature-large {
      grid-column: span 2;
    }

    @media (max-width: 768px) {
      .feature-grid {
        grid-template-columns: 1fr;
      }
      .feature-grid .feature-large {
        grid-column: span 1;
      }
    }