html {
     background: black;
     height:100%;
     min-height:100%;
 }
body {
    margin: 0px;
    padding: 0px;
    width: 100%;
    overflow: hidden;
}
body::after{
    position:absolute; width:0; height:0; overflow:hidden; z-index:-1;
    content:url(img/background/backgroundBlue.jpg) url(img/background/backgroundRed.jpg) url(img/background/backgroundYellow.jpg);
}
canvas {
    background: radial-gradient(ellipse, rgba(255,255,255,0.0), rgba(83,99,176,0.65)), url(img/background/backgroundBlue.jpg) repeat;
    display: block;
    margin-top: 0px;
    margin-left: auto;
    margin-right: auto;
    position: absolute;
}