body {
    background-color: #efefef;
    background-image: url(https://s1.ax1x.com/2020/03/15/81PmWt.png);
    background-repeat: no-repeat;
    background-attachment: fixed;
    background-position: center 0;
    background-size: cover;
    padding-top: 0px;
    opacity: 0.85 /* 设置虚化 */;
}