canvas {
  position: absolute;
  top: 0;
  left: 0;
}

@keyframes example {
  0% {
    background-color: rgb(0,123,255);
  }
  20% {
    background-color: limegreen;
  }
  40% {
    background-color: blue;
  }
  60% {
    background-color: red;
  }
  80% {
    background-color: gold;
  }
  100% {
    background-color: rgb(0,123,255);
  }
}