/* roulang page: index */
:root {
      --primary-deep: #0A2540;
      --accent-ocean: #00B4D8;
      --accent-hover: #0077B6;
      --white: #FFFFFF;
      --ice-gray: #F4F8FB;
      --text-body: #4A5B6E;
      --text-light: #B0C4DE;
      --border-light: #E9EEF3;
      --shadow-card: 0 8px 30px rgba(10, 37, 64, 0.06);
      --shadow-card-hover: 0 16px 40px rgba(10, 37, 64, 0.10);
      --shadow-btn: 0 8px 20px rgba(0, 180, 216, 0.3);
      --radius-card: 12px;
      --radius-btn: 8px;
      --font-stack: "PingFang SC", "Microsoft YaHei", "Helvetica Neue", Helvetica, Arial, sans-serif;
      --transition: 0.3s ease;
      --nav-width: 240px;
      --mobile-nav-height: 60px;
    }

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

    html {
      scroll-behavior: smooth;
    }

    body {
      font-family: var(--font-stack);
      background-color: var(--white);
      color: var(--text-body);
      line-height: 1.6;
      display: flex;
      flex-direction: row;
      min-height: 100vh;
    }

    /* 左侧竖向导航 (桌面) */
    .side-nav {
      position: fixed;
      top: 0;
      left: 0;
      width: var(--nav-width);
      height: 100vh;
      background-color: var(--primary-deep);
      display: flex;
      flex-direction: column;
      padding: 2rem 1.5rem;
      z-index: 100;
      box-shadow: 4px 0 20px rgba(0,0,0,0.08);
      transition: transform 0.3s ease;
      overflow-y: auto;
    }

    .nav-logo {
      font-size: 1.8rem;
      font-weight: 700;
      letter-spacing: 1px;
      color: var(--white);
      margin-bottom: 3rem;
      text-decoration: none;
      display: flex;
      align-items: center;
      gap: 0.5rem;
    }
    .nav-logo i {
      color: var(--accent-ocean);
      font-size: 2rem;
    }

    .nav-menu {
      list-style: none;
      display: flex;
      flex-direction: column;
      gap: 1.2rem;
      flex: 1;
    }

    .nav-menu a {
      color: var(--text-light);
      text-decoration: none;
      font-weight: 500;
      font-size: 1rem;
      display: flex;
      align-items: center;
      gap: 0.8rem;
      padding: 0.6rem 0.8rem;
      border-radius: 6px;
      transition: var(--transition);
    }

    .nav-menu a i {
      width: 20px;
      text-align: center;
    }

    .nav-menu a:hover,
    .nav-menu a.active {
      color: var(--accent-ocean);
      background-color: rgba(255,255,255,0.05);
    }

    .nav-footer-meta {
      margin-top: auto;
      color: var(--text-light);
      font-size: 0.75rem;
      opacity: 0.7;
    }

    /* 右侧主内容区 */
    .main-content {
      margin-left: var(--nav-width);
      width: calc(100% - var(--nav-width));
      background: var(--white);
    }

    /* 移动端顶部导航 */
    .mobile-nav {
      display: none;
      position: fixed;
      top: 0;
      left: 0;
      width: 100%;
      height: var(--mobile-nav-height);
      background: var(--primary-deep);
      justify-content: space-between;
      align-items: center;
      padding: 0 1.5rem;
      z-index: 110;
      box-shadow: 0 4px 12px rgba(0,0,0,0.1);
    }
    .mobile-logo {
      font-size: 1.4rem;
      font-weight: 700;
      color: white;
      text-decoration: none;
      display: flex;
      align-items: center;
      gap: 0.4rem;
    }
    .hamburger {
      background: none;
      border: none;
      color: white;
      font-size: 1.8rem;
      cursor: pointer;
    }
    .mobile-menu-overlay {
      position: fixed;
      top: 0;
      left: 0;
      width: 100%;
      height: 100%;
      background: var(--primary-deep);
      z-index: 105;
      display: flex;
      flex-direction: column;
      justify-content: center;
      align-items: center;
      gap: 2rem;
      transform: translateY(-100%);
      transition: transform 0.3s ease;
    }
    .mobile-menu-overlay.open {
      transform: translateY(0);
    }
    .mobile-menu-overlay a {
      color: var(--text-light);
      font-size: 1.5rem;
      text-decoration: none;
      font-weight: 500;
      transition: color 0.2s;
    }
    .mobile-menu-overlay a:hover {
      color: var(--accent-ocean);
    }

    /* 通用容器 */
    .container {
      max-width: 1200px;
      margin: 0 auto;
      padding: 0 2rem;
    }

    section {
      padding: 100px 0;
    }

    /* 板块背景交替 */
    .bg-ice {
      background-color: var(--ice-gray);
    }

    h1 {
      font-size: 48px;
      line-height: 56px;
      font-weight: 700;
      color: var(--primary-deep);
      letter-spacing: 0.5px;
    }
    h2 {
      font-size: 36px;
      line-height: 44px;
      font-weight: 600;
      color: var(--primary-deep);
      margin-bottom: 1rem;
      letter-spacing: 0.5px;
    }
    h3 {
      font-size: 20px;
      font-weight: 600;
      color: var(--primary-deep);
    }

    .section-subtitle {
      color: var(--text-body);
      font-size: 1.1rem;
      max-width: 700px;
      margin-bottom: 3rem;
    }

    .btn {
      display: inline-flex;
      align-items: center;
      justify-content: center;
      gap: 0.5rem;
      font-weight: 600;
      border-radius: var(--radius-btn);
      transition: var(--transition);
      text-decoration: none;
      cursor: pointer;
      border: none;
    }
    .btn-primary {
      background: var(--accent-ocean);
      color: white;
      padding: 14px 36px;
      box-shadow: 0 4px 12px rgba(0,180,216,0.2);
    }
    .btn-primary:hover {
      background: var(--accent-hover);
      box-shadow: var(--shadow-btn);
      transform: translateY(-2px);
    }
    .btn-outline {
      background: transparent;
      border: 2px solid var(--primary-deep);
      color: var(--primary-deep);
      padding: 12px 34px;
    }
    .btn-outline:hover {
      background: var(--primary-deep);
      color: white;
    }

    /* 卡片 */
    .card {
      background: var(--white);
      border-radius: var(--radius-card);
      box-shadow: var(--shadow-card);
      padding: 2rem;
      transition: var(--transition);
      border: 1px solid var(--border-light);
    }
    .card:hover {
      transform: translateY(-4px);
      box-shadow: var(--shadow-card-hover);
    }

    .grid-2, .grid-3 {
      display: grid;
      gap: 2rem;
    }
    .grid-2 { grid-template-columns: repeat(2, 1fr); }
    .grid-3 { grid-template-columns: repeat(3, 1fr); }

    /* 图文交替布局 */
    .split-row {
      display: flex;
      align-items: center;
      gap: 3rem;
    }
    .split-row.reverse {
      flex-direction: row-reverse;
    }
    .split-text {
      flex: 1;
    }
    .split-img {
      flex: 1;
    }
    .split-img img {
      width: 100%;
      border-radius: var(--radius-card);
      box-shadow: var(--shadow-card);
    }

    /* 数据大数字 */
    .stat-number {
      font-size: 48px;
      font-weight: 700;
      color: var(--primary-deep);
      line-height: 1.2;
    }
    .stat-label {
      color: var(--accent-ocean);
      font-weight: 600;
    }

    /* FAQ 手风琴 */
    .faq-item {
      border-bottom: 1px solid var(--border-light);
      padding: 1.2rem 0;
    }
    .faq-question {
      display: flex;
      justify-content: space-between;
      align-items: center;
      font-weight: 600;
      color: var(--primary-deep);
      cursor: pointer;
      font-size: 1.1rem;
    }
    .faq-answer {
      max-height: 0;
      overflow: hidden;
      transition: max-height 0.4s ease;
      color: var(--text-body);
    }
    .faq-answer.open {
      max-height: 200px;
      margin-top: 0.8rem;
    }

    .hero-bg {
      background-image: url('/assets/images/backpic/back-1.webp');
      background-size: cover;
      background-position: center;
      position: relative;
    }
    .hero-overlay {
      background: rgba(10,37,64,0.7);
      backdrop-filter: blur(2px);
    }

    footer {
      background: var(--primary-deep);
      color: var(--text-light);
      padding: 3rem 0;
    }

    @media (max-width: 1024px) {
      h1 { font-size: 38px; line-height: 46px; }
      h2 { font-size: 28px; }
      .grid-3 { grid-template-columns: repeat(2, 1fr); }
      .split-row { flex-direction: column; }
      .split-row.reverse { flex-direction: column; }
    }

    @media (max-width: 768px) {
      body {
        flex-direction: column;
      }
      .side-nav {
        display: none;
      }
      .mobile-nav {
        display: flex;
      }
      .main-content {
        margin-left: 0;
        width: 100%;
        padding-top: var(--mobile-nav-height);
      }
      .grid-2, .grid-3 { grid-template-columns: 1fr; }
      section { padding: 60px 0; }
      h1 { font-size: 32px; line-height: 40px; }
      h2 { font-size: 24px; }
      .container { padding: 0 1.5rem; }
    }