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

body {
    background-color: #222;
    margin: 0;
}

#drawing_canvas {
    background-color: #aaa;
    position: absolute;
    margin: auto;
    width: 1024px;
    height: 480px;
    top: 0;
    bottom: 0;
    left: 0;
    right: 0;
}