:root{--background-color: #000000}*{margin:0;padding:0}body{background-color:var(--background-color);overflow:hidden}#buttonToggleFullscreen{position:absolute;right:0;bottom:0;margin:0;padding:0;background-color:transparent;border:0;cursor:pointer;opacity:.5;color:#fff;transition:all .1s ease-in-out}#buttonToggleFullscreen:hover{opacity:1}