html, body, canvas {
  width: 100%;
  height: 100%;
  margin: 0;
  padding: 0;
  object-fit: contain;
  background: black;
}
button {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  border: none;
  background: white;
  color: black;
  font-size: 30px;
  padding: 10px 50px;
}