body{
    background-image: url("https://img2018.cnblogs.com/blog/1714605/201908/1714605-20190813191925133-1076534379.jpg");
    background-position: initial;
    background-size: cover;
    background-repeat: no-repeat;
    background-attachment: fixed;
    background-origin: initial;
    background-clip: initial;
    height:100%;
    width:100%;
    }