html, body {
    margin: 0;
    padding: 0;
    overflow: hidden;
    /* cool gradient backdrop: deep blues into teal */
    background: linear-gradient(135deg, #09203f 0%, #537895 100%);
}

canvas {
    position: fixed;
    top: 0; left: 0;
    width: 100vw;
    height: 100vh;
    background: transparent;
    display: block;
}