内嵌H5的canvas,iframe等块级元素为背景

html{height:100%;background-image:-webkit-radial-gradient(ellipse farthest-corner at center top,#000d4d 0,#000105 100%);background-image:radial-gradient(ellipse farthest-corner at center top,#000d4d 0,#000105 100%);cursor:url('http://testtp5.xyz/wp-content/uploads/2018/05/bitbug_favicon.ico'),auto}
body{width:100%;height:100%;margin:0;overflow:hidden}
iframe{top:0;left:0;height:100%;width:100%;position:absolute}
  *{margin:0px;padding:0px; font-family: "微软雅黑";}

可以适当添加z-index

附上一个国外大佬用js写的樱花飘落iframe