body {
 
  background-size: cover;
  background-attachment: fixed;
  background-position: center;
  margin: 0;
  font-family: "Microsoft YaHei", sans-serif;
}
html, body {
    margin: 0;
    padding: 0;
    height: 100%;
    width: 100%;
  }
 .video-bg-container {
    position: fixed;      /* 固定位置，不随滚动 */
    top: 0;
    left: 0;
    width: 100vw;         /* 确保占满整个可视宽度 */
    height: 100vh;        /* 确保占满整个可视高度 */
    overflow: hidden;
    z-index: -1;          /* 放在所有内容下方 */
    background: black;    /* 视频加载前的背景 */
  }
 .bg-video {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    object-fit: cover;    /* 保持比例同时裁剪铺满整个区域 */
    object-position: center; /* 居中裁切 */
    z-index: -1;
    pointer-events: none;
  }

  /* 可选：添加一层暗遮罩增强可读性 */
  .video-bg-container::after {
    content: "";
    position: absolute;
    inset: 0;
    background: rgba(0,0,0,0.1);
    z-index: 0
  }

li a {
    display: block;
    color: #000;
    padding: 8px 16px;
    text-decoration: none;
}
li a:hover {
    background-color: #555;
    color: white;
}
li{
	float:left;
}
ul a {
    color: #000;
    text-decoration: none;
}
ul a:hover {
    color: white;
}
ul{
	padding: 0;
}
.header {
  background-color: rgb(236, 236, 236,0.7);
  padding: 15px;
   margin-bottom: 20px;
  border-radius: 10px;
  box-shadow: 0 4px 10px rgba(0,0,0,0.1);
  text-align: center;
}
.card {
  background-color: rgba(236, 236, 236, 0.8);
  padding: 20px;
  margin-bottom: 20px;
  border-radius: 10px;
  box-shadow: 0 4px 10px rgba(0,0,0,0.1);
}
.row {
  display: flex;              /* 关键：flex 布局 */
  justify-content: center;    /* 居中整个行 */
  gap: 20px;                  /* 左右间距 */
  padding: 20px;
  flex-wrap: nowrap;          /* 不自动换行 */
}

.leftcolumn {
  flex: 1 1 60%;
}

.rightcolumn {
  flex: 1 1 30%;
}