/* roulang page: index */
/* 设计变量与全局重置 */
    :root {
      --color-black: #0A0C0F;
      --color-white: #FFFFFF;
      --color-off-white: #F4F5F7;
      --color-accent: #FF4F00;
      --color-gray-dark: #2C2E33;
      --color-gray-mid: #7A7E85;
      --color-gray-light: #D1D5DB;
      --color-border: #E5E7EB;
      --font-heading: 'PingFang SC', 'Microsoft YaHei', sans-serif;
      --font-body: 'PingFang SC', 'Microsoft YaHei', sans-serif;
      --font-data: 'DIN Alternate', 'Impact', sans-serif;
      --shadow-hard: 4px 4px 0px rgba(0,0,0,0.08);
      --transition-smooth: cubic-bezier(0.25, 0.46, 0.45, 0.94);
    }
    
    * {
      box-sizing: border-box;
      margin: 0;
      padding: 0;
    }
    
    html {
      scroll-behavior: smooth;
    }
    
    body {
      font-family: var(--font-body);
      background-color: var(--color-off-white);
      color: var(--color-black);
      line-height: 1.8;
      letter-spacing: 0.01em;
      -webkit-font-smoothing: antialiased;
      -moz-osx-font-smoothing: grayscale;
    }
    
    /* 自定义字体替代方案 */
    .font-heading {
      font-family: var(--font-heading);
      font-weight: 700;
      letter-spacing: -0.02em;
    }
    
    .font-data {
      font-family: var(--font-data);
      font-weight: 700;
    }
    
    /* 容器最大宽度与网格 */
    .container-custom {
      max-width: 1440px;
      margin-left: auto;
      margin-right: auto;
      padding-left: 2rem;
      padding-right: 2rem;
    }
    
    @media (max-width: 768px) {
      .container-custom {
        padding-left: 1.5rem;
        padding-right: 1.5rem;
      }
    }
    
    /* 导航品牌行 */
    .brand-row {
      border-bottom: 1px solid rgba(0,0,0,0.05);
      background: var(--color-white);
    }
    
    .logo-text {
      font-family: var(--font-heading);
      font-weight: 900;
      letter-spacing: 0.2em;
      font-size: 1.5rem;
      color: var(--color-black);
      text-transform: uppercase;
    }
    
    /* 频道标签行 */
    .channel-nav a {
      font-size: 0.95rem;
      font-weight: 500;
      color: var(--color-gray-mid);
      padding-bottom: 0.5rem;
      border-bottom: 2px solid transparent;
      transition: color 0.2s, border-color 0.2s;
      letter-spacing: 0.02em;
    }
    
    .channel-nav a:hover {
      color: var(--color-black);
      border-bottom-color: var(--color-accent);
    }
    
    .channel-nav a.active {
      color: var(--color-black);
      border-bottom-color: var(--color-accent);
    }
    
    /* 移动端汉堡菜单 */
    .mobile-menu-panel {
      position: fixed;
      top: 0;
      right: -100%;
      width: 80%;
      max-width: 320px;
      height: 100vh;
      background: var(--color-white);
      box-shadow: -8px 0 20px rgba(0,0,0,0.05);
      transition: right 0.35s var(--transition-smooth);
      z-index: 1000;
      display: flex;
      flex-direction: column;
      padding: 2rem;
    }
    
    .mobile-menu-panel.open {
      right: 0;
    }
    
    .menu-backdrop {
      position: fixed;
      inset: 0;
      background: rgba(0,0,0,0.3);
      z-index: 999;
      opacity: 0;
      pointer-events: none;
      transition: opacity 0.25s;
    }
    
    .menu-backdrop.show {
      opacity: 1;
      pointer-events: auto;
    }
    
    /* 按钮组件 */
    .btn-primary {
      background: var(--color-accent);
      color: white;
      font-weight: 600;
      padding: 0.9rem 2.2rem;
      border-radius: 2px;
      display: inline-flex;
      align-items: center;
      justify-content: center;
      transition: background 0.2s, transform 0.15s;
      letter-spacing: 0.03em;
      border: none;
      cursor: pointer;
      box-shadow: var(--shadow-hard);
    }
    
    .btn-primary:hover {
      background: #E04400;
      transform: translateX(2px);
    }
    
    .btn-outline {
      background: transparent;
      color: white;
      border: 1px solid white;
      padding: 0.9rem 2.2rem;
      border-radius: 2px;
      font-weight: 600;
      transition: background 0.2s, color 0.2s, transform 0.15s;
      letter-spacing: 0.03em;
      display: inline-flex;
      align-items: center;
    }
    
    .btn-outline:hover {
      background: white;
      color: var(--color-black);
      transform: translateX(2px);
    }
    
    /* 卡片直角与阴影 */
    .card-hard {
      background: white;
      border: 1px solid var(--color-border);
      border-radius: 0px;
      box-shadow: none;
      transition: border-color 0.2s;
    }
    
    .card-hard:hover {
      border-color: var(--color-black);
    }
    
    /* 服务图文区图片容器 */
    .img-frame {
      border: 1px solid var(--color-black);
      border-radius: 0px;
      overflow: hidden;
    }
    
    /* 数据数字样式 */
    .stat-number {
      font-family: var(--font-data);
      font-size: 3.5rem;
      line-height: 1;
      color: var(--color-black);
    }
    
    /* FAQ 动画 */
    .faq-answer {
      max-height: 0;
      overflow: hidden;
      transition: max-height 0.4s ease;
    }
    
    .faq-item.open .faq-answer {
      max-height: 300px;
    }
    
    .faq-icon {
      transition: transform 0.3s ease;
    }
    
    .faq-item.open .faq-icon {
      transform: rotate(45deg);
    }
    
    /* 滚动淡入 */
    .fade-up {
      opacity: 0;
      transform: translateY(20px);
      transition: opacity 0.7s var(--transition-smooth), transform 0.7s var(--transition-smooth);
    }
    
    .fade-up.visible {
      opacity: 1;
      transform: translateY(0);
    }
    
    /* 页脚水印 */
    .footer-watermark {
      font-family: var(--font-heading);
      font-weight: 900;
      font-size: 5rem;
      opacity: 0.05;
      color: white;
      letter-spacing: 0.1em;
      line-height: 1;
      user-select: none;
    }
    
    @media (max-width: 1024px) {
      .stat-number {
        font-size: 2.8rem;
      }
      .channel-nav {
        display: none;
      }
      .mobile-menu-trigger {
        display: flex;
      }
    }
    
    @media (min-width: 1025px) {
      .mobile-menu-trigger {
        display: none;
      }
      .channel-nav {
        display: flex;
      }
    }