/* 1. 基础重置 & 变量定义 */
    :root {
      --brand: #0d6efd;
      --brand-dark: #0b5ed7;
      --ink: #111827;
      --muted: #6b7280;
      --bg: #f8fafc;
      --card: #ffffff;
      --line: #e5e7eb;
      --logo: #0B3D91;
      --shadow: 0 4px 20px rgba(0,0,0,.08);
      --shadow-hover: 0 8px 30px rgba(0,0,0,.12);
      --radius: 12px;
      --transition: all 0.3s ease;
      --sidebar-width: 80%;
      --sidebar-max-width: 320px;
    }

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

    html, body {
      color: var(--ink);
      font-family: system-ui, -apple-system, Segoe UI, Roboto, Helvetica, Arial, "Noto Sans JP", "Hiragino Kaku Gothic ProN", Meiryo, sans-serif;
      background: var(--bg);
      line-height: 1.7;
      scroll-behavior: smooth; /* 平滑滚动 */
    }

    /* 2. 通用组件样式 */
    .wrap {
      max-width: 1200px;
      margin: 0 auto;
      padding: 0 20px;
    }

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

    a:hover {
      color: var(--brand-dark);
    }

    img {
      max-width: 100%;
      height: auto;
      border-radius: var(--radius);
      display: block;
      object-fit: cover;
    }

    .btn {
      display: inline-block;
      padding: 0.75rem 1.5rem;
      background: var(--brand);
      color: #fff !important;
      border-radius: 8px;
      font-weight: 600;
      border: none;
      cursor: pointer;
      transition: var(--transition);
      text-align: center;
    }

    .btn:hover {
      background: var(--brand-dark);
      transform: translateY(-2px);
      box-shadow: 0 4px 12px rgba(13, 110, 253, 0.3);
    }

    .btn-outline {
      background: transparent;
      color: var(--brand) !important;
      border: 1px solid var(--brand);
    }

    .btn-outline:hover {
      background: var(--brand);
      color: #fff !important;
    }

    .kicker {
      color: var(--brand);
      font-weight: 700;
      font-size: 12px;
      letter-spacing: 0.08em;
      text-transform: uppercase;
      display: block;
      margin-bottom: 8px;
    }

    h1 {
      font-size: clamp(28px, 5vw, 44px);
      line-height: 1.25;
      margin-bottom: 1.5rem;
      color: var(--ink);
    }

    h2 {
      font-size: clamp(22px, 4vw, 32px);
      line-height: 1.3;
      margin-bottom: 1.2rem;
      color: var(--ink);
    }

    h3 {
      font-size: 18px;
      margin-bottom: 1rem;
      color: var(--ink);
    }

    p {
      color: var(--muted);
      margin-bottom: 1.2rem;
    }

    .lead {
      font-size: clamp(16px, 2vw, 18px);
      color: var(--muted);
      margin-bottom: 2rem;
    }

    .grid {
      display: grid;
      gap: 24px;
    }

    .card {
      background: var(--card);
      border: 1px solid var(--line);
      border-radius: var(--radius);
      padding: 28px;
      box-shadow: var(--shadow);
      transition: var(--transition);
    }

    .card:hover {
      box-shadow: var(--shadow-hover);
      transform: translateY(-5px);
    }

    section {
      padding: 80px 0;
    }

    /* 3. 头部导航样式 */
    header {
      position: sticky;
      top: 0;
      z-index: 90;
      background: #fff;
      border-bottom: 1px solid var(--line);
      padding: 0.75rem 0;
    }

    .nav-container {
      display: flex;
      align-items: center;
      justify-content: space-between;
      height: 56px;
    }

    .logo {
      font-weight: 800;
      font-size: 22px;
      color: var(--logo);
    }

    /* 桌面端导航 */
    .desktop-nav {
      display: flex;
      gap: 28px;
    }

    .desktop-nav a {
      color: var(--ink);
      font-weight: 500;
      font-size: 15px;
      padding: 4px 0;
      position: relative;
    }

    .desktop-nav a::after {
      content: "";
      position: absolute;
      bottom: 0;
      left: 0;
      width: 0;
      height: 2px;
      background: var(--brand);
      transition: var(--transition);
    }

    .desktop-nav a:hover::after,
    .desktop-nav a.active::after {
      width: 100%;
    }
    .desktop-nav .btn{padding:5px 15px;}
    /* 移动端菜单按钮 */
    .menu-btn {
      display: none;
      background: transparent;
      border: none;
      font-size: 24px;
      color: var(--ink);
      cursor: pointer;
    }

    /* 移动端侧边栏 */
    .mobile-sidebar {
      position: fixed;
      top: 0;
      right: 0;
      width: var(--sidebar-width);
      max-width: var(--sidebar-max-width);
      height: 100vh;
      background: var(--card);
      box-shadow: -4px 0 20px rgba(0,0,0,.1);
      z-index: 999;
      transform: translateX(100%); /* 初始隐藏 */
      transition: transform 0.3s ease;
      padding: 2rem;
      overflow-y: auto;
    }

    .mobile-sidebar.open {
      transform: translateX(0); /* 打开时滑入 */
    }

    .sidebar-header {
      display: flex;
      justify-content: space-between;
      align-items: center;
      margin-bottom: 2rem;
    }

    .close-btn {
      background: transparent;
      border: none;
      font-size: 24px;
      color: var(--ink);
      cursor: pointer;
    }

    .mobile-nav {
      display: flex;
      flex-direction: column;
      gap: 1.5rem;
    }

    .mobile-nav a {
      color: var(--ink);
      font-weight: 500;
      font-size: 16px;
      padding: 8px 0;
      border-bottom: 1px solid var(--line);
    }

    .mobile-nav a:hover {
      color: var(--brand);
    }

    /* 遮罩层 */
    .overlay {
      position: fixed;
      top: 0;
      left: 0;
      width: 100%;
      height: 100vh;
      background: rgba(0,0,0,.5);
      z-index: 998;
      display: none;
      transition: var(--transition);
    }

    .overlay.show {
      display: block;
    }

    /* Footer区块 */
    .footer {
      padding: 40px 0;
      background: #fff;
      border-top: 1px solid var(--line);
      color: var(--muted);
      font-size: 14px;
    }

    .footer-links {
      display: flex;
      gap: 20px;
      margin-bottom: 1.5rem;
      flex-wrap: wrap;
    }

    .footer-links a {
      color: var(--muted);
    }

    .footer-links a:hover {
      color: var(--brand);
    }

    .copyright {
      font-size: 13px;
    }

    /* 5. 响应式适配（768px以下） */
    @media (max-width: 768px) {
      /* 导航适配 */
      .desktop-nav {
        display: none;
      }

      .menu-btn {
        display: block;
      }

      /* 网格布局适配 */
      .grid {
        grid-template-columns: 1fr !important;
      }

      .hero-grid {
        grid-template-columns: 1fr !important;
      }

      .hero-img {
        order: -1; /* 移动端图片在上 */
      }

      /* 内边距调整 */
      section {
        padding: 60px 0;
      }

      .hero {
        padding: 80px 0;
      }

      /* 按钮适配 */
      .btn {
        width: 100%;
      }

      /* Footer适配 */
      .footer-links {
        flex-direction: column;
        gap: 12px;
      }
    }

    /* 桌面端网格布局 */
    @media (min-width: 769px) {
      .cols-2 {
        grid-template-columns: repeat(2, 1fr);
      }

      .cols-3 {
        grid-template-columns: repeat(3, 1fr);
      }

      .hero-grid {
        grid-template-columns: 1.1fr 0.9fr;
      }
    }

    /* 6. 动画效果 */
    .fade-in {
      opacity: 0;
      transform: translateY(20px);
      transition: opacity 0.6s ease, transform 0.6s ease;
    }

    .fade-in.visible {
      opacity: 1;
      transform: translateY(0);
    }

  /* 返回顶部按钮样式 */
  .back-to-top {
    position: fixed;
    bottom: 30px;
    right: 30px;
    width: 50px;
    height: 50px;
    border-radius: 50%;
    background: var(--brand);
    color: white;
    border: none;
    box-shadow: 0 4px 12px rgba(37, 99, 235, 0.3);
    font-size: 20px;
    cursor: pointer;
    display: none; /* 初始隐藏 */
    align-items: center;
    justify-content: center;
    transition: all 0.3s ease;
    z-index: 100;
  }

  .back-to-top:hover {
    background: var(--brand-ink);
    color:var(--brand); 
    transform: translateY(-3px);
    box-shadow: 0 6px 16px rgba(37, 99, 235, 0.4);
  }

  .back-to-top.show {
    display: flex; /* 显示按钮 */
  }