html,
body {
  background-color: #f8f9fa;
  margin: 0;
  padding: 0;
  display: flex;
  align-items: center; /* vertical */
  justify-content: center; /* horizontal */
}
canvas {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  filter: drop-shadow(0px 0px 2vmax #00000040)
}