html,
body{
    margin:0;
    padding:0;
    width:100%;
    height:100%;
    overflow:hidden;
}

#cover,
#framePlayer,
#mainVideo{
    position:fixed;
    inset:0;
    width:100vw;
    height:100vh;
    object-fit:cover;
}

#mainVideo,
#framePlayer{
    display:none;
}