body{margin:0;overflow:hidden;font-family:Arial,sans-serif}#startScreen{position:absolute;top:0;left:0;width:100%;height:100%;background:#000000b3;color:#fff;display:flex;flex-direction:column;justify-content:center;align-items:center;z-index:10}#startScreen button{padding:10px 20px;font-size:16px;margin-top:20px;cursor:pointer}