#canvas1 {
    width: 800px;
    height: 600px;
    /* margin: 2% auto; */
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    background-color: #ccc;
}

html, body {
    margin: 0;
    padding: 0;
    background-color: #474747;
}