html, body {
    margin: 0;
    padding: 0;
    width: 100%;
    height: 100%;
    overflow: hidden;
    background: transparent;   /* <-- make background white */
}

#bg-canvas {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    display: block;
    pointer-events: none;  /* keep clicks working */
    z-index: -1; 
}