/* roulang page: index */
/* 设计变量与全局重置 */
    :root {
      --primary: #F15A24;
      --primary-hover: #D14A1A;
      --primary-soft: rgba(241, 90, 36, 0.1);
      --dark: #1E2A38;
      --dark-soft: #2A3848;
      --gray-text: #5A6B7F;
      --gray-light: #8E9BAA;
      --bg-light: #F8F9FC;
      --bg-warm: #FFF9F5;
      --white: #FFFFFF;
      --border-light: #E9ECF0;
      --shadow-card: 0 2px 12px rgba(0,0,0,0.04);
      --shadow-hover: 0 6px 20px rgba(0,0,0,0.08);
      --radius-card: 12px;
      --radius-btn: 8px;
      --radius-input: 6px;
      --font-sans: 'PingFang SC', 'Microsoft YaHei', 'Hiragino Sans GB', 'Inter', system-ui, -apple-system, sans-serif;
      --transition: 0.25s ease;
    }
    * {
      margin: 0;
      padding: 0;
      box-sizing: border-box;
    }
    html {
      scroll-behavior: smooth;
      font-size: 16px;
    }
    body {
      font-family: var(--font-sans);
      background: var(--white);
      color: var(--dark);
      line-height: 1.7;
      -webkit-font-smoothing: antialiased;
    }
    img {
      max-width: 100%;
      display: block;
      height: auto;
    }
    a {
      text-decoration: none;
      color: inherit;
      transition: var(--transition);
    }
    button, .btn {
      cursor: pointer;
      font-family: inherit;
      border: none;
      background: none;
      transition: var(--transition);
      display: inline-flex;
      align-items: center;
      justify-content: center;
      gap: 8px;
      font-weight: 600;
    }
    .container {
      max-width: 1200px;
      margin: 0 auto;
      padding: 0 24px;
      width: 100%;
    }
    section {
      padding: 5rem 0;
    }
    @media (max-width: 768px) {
      section {
        padding: 3.5rem 0;
      }
      .container {
        padding: 0 20px;
      }
    }

    /* 导航栏 */
    .site-header {
      position: fixed;
      top: 0;
      left: 0;
      width: 100%;
      z-index: 1000;
      height: 72px;
      background: transparent;
      transition: background 0.3s ease, box-shadow 0.3s ease;
      display: flex;
      align-items: center;
    }
    .site-header.scrolled {
      background: rgba(255,255,255,0.9);
      backdrop-filter: blur(12px);
      box-shadow: 0 1px 0 var(--border-light);
    }
    .header-inner {
      display: flex;
      align-items: center;
      justify-content: space-between;
      width: 100%;
    }
    .logo {
      font-size: 1.5rem;
      font-weight: 700;
      color: var(--dark);
      display: flex;
      align-items: center;
      gap: 6px;
    }
    .logo span {
      color: var(--primary);
    }
    .nav-links {
      display: flex;
      align-items: center;
      gap: 2rem;
    }
    .nav-links a {
      font-weight: 500;
      color: var(--dark);
      position: relative;
      padding: 4px 0;
      font-size: 0.95rem;
    }
    .nav-links a::after {
      content: '';
      position: absolute;
      bottom: -4px;
      left: 0;
      width: 0;
      height: 2px;
      background: var(--primary);
      transition: width 0.2s ease;
    }
    .nav-links a:hover,
    .nav-links a.active {
      color: var(--primary);
    }
    .nav-links a.active::after {
      width: 100%;
    }
    .btn-primary {
      background: var(--primary);
      color: white;
      padding: 10px 24px;
      border-radius: var(--radius-btn);
      font-weight: 600;
      white-space: nowrap;
      min-width: 110px;
      min-height: 44px;
    }
    .btn-primary:hover {
      background: var(--primary-hover);
      transform: translateY(-2px);
      box-shadow: 0 8px 16px rgba(241,90,36,0.25);
    }
    .btn-outline {
      border: 1.5px solid var(--primary);
      color: var(--primary);
      background: transparent;
      padding: 10px 24px;
      border-radius: var(--radius-btn);
      font-weight: 600;
      min-height: 44px;
    }
    .btn-outline:hover {
      background: var(--primary-soft);
      transform: translateY(-2px);
    }
    .hamburger {
      display: none;
      flex-direction: column;
      gap: 5px;
      cursor: pointer;
      background: none;
      border: none;
    }
    .hamburger span {
      width: 24px;
      height: 2px;
      background: var(--dark);
      transition: 0.3s;
    }
    .mobile-menu {
      display: none;
      position: fixed;
      top: 0;
      left: 0;
      width: 100%;
      height: 100%;
      background: var(--dark);
      flex-direction: column;
      align-items: center;
      justify-content: center;
      gap: 2.5rem;
      z-index: 999;
    }
    .mobile-menu a {
      color: white;
      font-size: 1.3rem;
      font-weight: 500;
    }
    .mobile-menu .btn-primary {
      background: var(--primary);
      color: white;
    }
    @media (max-width: 992px) {
      .nav-links { display: none; }
      .hamburger { display: flex; }
    }