body #background_cover{position:fixed;width:100vw;height:100vh;z-index:-1}body #background_cover::before{position:fixed;top:0;left:0;z-index:-1;width:100vw;height:100vh;background-image:url(../img/MainEnter_background.jpg?20240313001);background-position:center;background-size:cover;background-repeat:no-repeat;content:""}