:-moz-full-screen canvas {
    position: absolute;
    top: 0; left: 0; right: 0; bottom: 0;
    margin: auto;
    width: 90%;
    height: 50%;
    box-shadow: 0px 0px 4px black;
    background-color: black;
}
:-webkit-full-screen canvas {
    position: absolute;
    top: 0; left: 0; right: 0; bottom: 0;
    margin: auto;
    width: 90%;
    height: 50%;
    box-shadow: 0px 0px 4px black;
    background-color: black;
}