background-canvas {

  z-index: -7;

}

canvas {
  display: block;
  margin: auto;
  position :absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  
  image-rendering: optimizeSpeed;
  image-rendering: -moz-crisp-edges;
  image-rendering: -webkit-optimize-contrast;
  image-rendering: optimize-contrast
}