html,body {
    margin: 0;
    padding: 0;
  background: #222;
}

main {
    text-align: center;
    width: 100%;
}

canvas {
    max-width: 100%;
    max-height: 100%;
    margin: auto;
    overflow: auto;
    position: fixed;
    object-fit: contain;
    top: 0;
    bottom: 0;
    left: 0;
    right: 0;
}


main {
  align-items: center;
  display: flex;
  height: 100vh; /* Fallback for browsers that do not support Custom Properties */
  justify-content: center;
}
main canvas {
  height: auto !important;
  width: auto !important;
  max-width: 100%;
  max-height: 100%;
  display: inline-block; /* Instead of display: block; */
  margin: 0 auto;
  vertical-align: middle;
  touch-action: none;
}