body{margin:0;background:#000}body::before{content:"";position:fixed;inset:0;z-index:-200;background:url("../img/bg.png") center/cover no-repeat}video{position:fixed;top:50%;left:50%;min-width:100%;min-height:100%;width:auto;height:auto;z-index:-100;transform:translateX(-50%) translateY(-50%);transition:opacity 1s}