body {
    font-size: 15px;
    padding: 0;
    margin: 0;
    font-family: "微软雅黑","宋体",Arial;
    width: 100%;
    height: 100%;
    background: #205424 url(https://images.cnblogs.com/cnblogs_com/helloyoyo/2004109/o_2108040311341001116W75SJ674A.png) no-repeat top 
    center fixed;
    background-size: cover;
  }