body, html {
    width: 100%;
    height: 100%;
    margin: 0;
    padding: 0;
    background-color: black;
    overflow-y: hidden;
}
canvas, div {
    background-color: #333;
    display: block;
}
.center {
    position: absolute;
    left: 50%;
    top: 50%;
    transform: translateX(-50%) translateY(-50%);
}