body { background: #eee; }

canvas {
    display: block;
    margin: auto auto;
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    box-shadow: -2px -2px 2px #EFEFEF, 5px 5px 5px #B9B9B9;
}

#div1 { width:100%; left: 50%; position: absolute; top: 50%; transform: translate(-50%, -50%);}