body {
    margin: 0;
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI",
      "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
    background-color: #ffffff;
    color: #333;
  }
  
  .title {
    font-size: 32px;
    font-weight: 600;
    margin-bottom: 8px;
  }
  
  .subtitle {
    font-size: 16px;
    color: #666;
    margin-bottom: 32px;
  }
  
  /* 搜索框 */
  .search-box {
    display: flex;
    justify-content: center;
    margin-bottom: 24px;
  }
  
  .search-box input {
    width: 100%;
    max-width: 520px;
    padding: 12px 16px;
    font-size: 14px;
    border: 1px solid #ddd;
    border-radius: 8px;
    outline: none;
  }
  
  .search-box input:focus {
    border-color: #1677ff;
  }
  
  /* Tabs */
  .tabs {
    display: flex;
    justify-content: center;
    gap: 24px;
  }
  
  .tab {
    text-decoration: none;
    color: #666;
    font-size: 16px;
    padding-bottom: 6px;
    position: relative;
  }
  
  .tab:hover {
    color: #1677ff;
  }
  
  .tab.active {
    color: #1677ff;
    font-weight: 600;
  }
  
  .tab.active::after {
    content: "";
    position: absolute;
    left: 0;
    bottom: 0;
    width: 100%;
    height: 2px;
    background-color: #1677ff;
    border-radius: 1px;
  }
  
  /* 教学中心内容区 */
.teaching-center {
    max-width: 960px;
    margin: 0 auto;
    padding: 32px 24px 40px;
    text-align: center;
  }
  
  .teaching-header .title {
    font-size: 32px;
    font-weight: 600;
    margin-bottom: 8px;
  }
  
  .teaching-header .subtitle {
    font-size: 16px;
    color: #666;
    margin-bottom: 32px;
  }
  
  /* ===== 全局 Header 修复 ===== */
.global-header {
    justify-content: space-between;
    align-items: center;
  
    padding: 16px 24px;
    border-bottom: 1px solid #eee;
    background-color: #fff;
  }
  .global-header-inner {
    max-width: 960px;
    margin: 0 auto;
    height: 64px;
  
    position: relative; /* 关键 */
  }
  
  
  
  /* 左侧导航 */
  .nav-left {
    position: absolute;
    left: 50%;
    top: 50%;
    transform: translate(-50%, -50%);
  
    display: flex;
    gap: 24px;
  }
  
  
  /* 右侧功能入口 */
  .nav-right {
    position: absolute;
    right: 0;
    top: 50%;
    transform: translateY(-50%);
  
    display: flex;
    gap: 16px;
  }
  
  
  /* 通用链接样式 */
  .nav-item,
  .nav-action {
    text-decoration: none;
    color: #333;
    font-size: 16px;
    white-space: nowrap;
  }
  
  .nav-item:hover,
  .nav-action:hover {
    color: #1677ff;
  }
  
  /* 选中态 */
  .nav-item.active {
    color: #1677ff;
    font-weight: 600;
    position: relative;
  }
  
  .nav-item.active::after {
    content: "";
    position: absolute;
    left: 0;
    bottom: -6px;
    width: 100%;
    height: 2px;
    background-color: #1677ff;
  }