body {
  background: linear-gradient(to right bottom, red, green, blue);
  width: 100vw;
  height: 100vh;
  overflow: hidden;
  margin: 0;
}
#canvas1 {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
}
#collision {
  opacity: 0
}