/* 背景 */
body:before {
    background: url(https://img2023.cnblogs.com/blog/2357111/202309/2357111-20230911211258742-1633739425.png) center/cover no-repeat;
    content: '';
    background-repeat: no-repeat;
    background-position: center;
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    z-index: -1;
   opacity: 1;
   -webkit-filter: grayscale(40%);
   -moz-filter: grayscale(40%);
   -ms-filter: grayscale(40%);
   -o-filter: grayscale(40%);
   filter: grayscale(40%);
   filter: gray;
}
/* 中心内容区域 */
#home {
   opacity: 0.6;
   border-radius: 10px;
}