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%);
}

canvas { touch-action: none; }
.source-notice { position: fixed; bottom: 3px; left: 8px; z-index: 2; color: #aaa; font: 10px sans-serif; }
.source-notice a { color: inherit; }