/* roulang page: index */
/* 设计变量与全局重置 */
    :root {
      --primary-deep: #0B1A3A;
      --primary-gradient: linear-gradient(135deg, #0B1A3A 0%, #132B52 100%);
      --accent-cyan: #00C2E0;
      --accent-cyan-hover: #00A8C4;
      --energy-orange: #FF6B35;
      --energy-orange-hover: #E55A2B;
      --bg-light: #F8FAFC;
      --card-white: #FFFFFF;
      --text-main: #1E293B;
      --text-secondary: #64748B;
      --text-on-dark: #F1F5F9;
      --border-light: #E2E8F0;
      --radius-card: 12px;
      --radius-btn: 8px;
      --radius-large: 16px;
      --shadow-card: 0 4px 24px rgba(0,0,0,0.06);
      --shadow-card-hover: 0 8px 32px rgba(0,0,0,0.12);
      --shadow-btn-cyan: 0 4px 16px rgba(0,194,224,0.3);
      --shadow-btn-orange: 0 6px 24px rgba(255,107,53,0.35);
      --transition-base: all 0.25s ease;
    }
    * {
      margin: 0;
      padding: 0;
      box-sizing: border-box;
    }
    body {
      font-family: 'PingFang SC', 'Microsoft YaHei', 'Noto Sans SC', system-ui, -apple-system, sans-serif;
      background-color: var(--bg-light);
      color: var(--text-main);
      line-height: 1.7;
      font-size: 16px;
      -webkit-font-smoothing: antialiased;
    }
    img {
      max-width: 100%;
      height: auto;
      display: block;
    }
    a {
      text-decoration: none;
      color: inherit;
      transition: var(--transition-base);
    }
    button, .btn {
      cursor: pointer;
      font-family: inherit;
      transition: var(--transition-base);
      display: inline-flex;
      align-items: center;
      justify-content: center;
      gap: 8px;
      border: none;
      font-weight: 600;
    }
    .container {
      max-width: 1280px;
      margin: 0 auto;
      padding: 0 24px;
    }
    /* 导航栏样式 */
    #main-header {
      position: fixed;
      top: 0;
      left: 0;
      width: 100%;
      z-index: 50;
      transition: background 0.3s, box-shadow 0.3s;
      background: transparent;
    }
    #main-header.scrolled {
      background: rgba(255,255,255,0.98);
      backdrop-filter: blur(8px);
      box-shadow: 0 1px 6px rgba(0,0,0,0.08);
    }
    #main-header .nav-logo {
      font-weight: 800;
      font-size: 1.6rem;
      letter-spacing: 0.5px;
      color: white;
      transition: color 0.3s;
    }
    #main-header.scrolled .nav-logo {
      color: var(--primary-deep);
    }
    #main-header .nav-link {
      color: rgba(255,255,255,0.9);
      font-weight: 500;
      transition: color 0.2s;
    }
    #main-header.scrolled .nav-link {
      color: var(--text-main);
    }
    #main-header .nav-link:hover,
    #main-header.scrolled .nav-link:hover {
      color: var(--accent-cyan);
    }
    .mobile-menu-btn {
      color: white;
      transition: color 0.3s;
    }
    #main-header.scrolled .mobile-menu-btn {
      color: var(--primary-deep);
    }
    /* Hero 区域渐变背景 */
    .hero-gradient {
      background: var(--primary-gradient);
      position: relative;
      overflow: hidden;
    }
    .hero-gradient::before {
      content: "";
      position: absolute;
      top: -20%;
      right: -10%;
      width: 70%;
      height: 120%;
      background: radial-gradient(circle at 80% 50%, rgba(0,194,224,0.15) 0%, transparent 60%);
      pointer-events: none;
    }
    /* 卡片系统 */
    .card-elevate {
      background: var(--card-white);
      border-radius: var(--radius-card);
      box-shadow: var(--shadow-card);
      transition: transform 0.2s, box-shadow 0.25s;
    }
    .card-elevate:hover {
      transform: translateY(-5px);
      box-shadow: var(--shadow-card-hover);
    }
    /* 方案对比右列高亮 */
    .scheme-highlight {
      background: #F0F9FF;
      border: 1px solid rgba(0,194,224,0.25);
      box-shadow: 0 10px 28px rgba(0,194,224,0.12);
      transform: scale(1.02);
    }
    /* FAQ 手风琴 */
    .faq-item {
      border-bottom: 1px solid var(--border-light);
      padding: 20px 0;
    }
    .faq-question {
      cursor: pointer;
      display: flex;
      justify-content: space-between;
      align-items: center;
      font-weight: 700;
      font-size: 1.1rem;
    }
    .faq-answer {
      max-height: 0;
      overflow: hidden;
      transition: max-height 0.35s ease, padding 0.3s;
      color: var(--text-secondary);
    }
    .faq-item.active .faq-answer {
      max-height: 200px;
      padding-top: 12px;
    }
    /* 按钮定义 */
    .btn-primary {
      background: var(--accent-cyan);
      color: white;
      border-radius: var(--radius-btn);
      padding: 12px 28px;
      box-shadow: var(--shadow-btn-cyan);
    }
    .btn-primary:hover {
      background: var(--accent-cyan-hover);
      box-shadow: 0 6px 18px rgba(0,194,224,0.4);
    }
    .btn-outline {
      background: transparent;
      border: 2px solid var(--accent-cyan);
      color: var(--accent-cyan);
      border-radius: var(--radius-btn);
      padding: 12px 28px;
    }
    .btn-outline:hover {
      background: #E6FAFD;
    }
    .btn-cta-large {
      background: var(--energy-orange);
      color: white;
      border-radius: 12px;
      padding: 18px 42px;
      font-size: 1.2rem;
      box-shadow: var(--shadow-btn-orange);
    }
    .btn-cta-large:hover {
      background: var(--energy-orange-hover);
      transform: scale(1.02);
    }
    /* 移动端菜单 */
    .mobile-menu {
      display: none;
      position: fixed;
      top: 0;
      left: 0;
      width: 100%;
      height: 100%;
      background: rgba(11,26,58,0.98);
      backdrop-filter: blur(12px);
      z-index: 100;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      gap: 2rem;
    }
    .mobile-menu.open {
      display: flex;
    }
    @media (max-width: 768px) {
      .container {
        padding: 0 20px;
      }
      h1 { font-size: 2.2rem; }
      h2 { font-size: 1.8rem; }
    }