body, html {
  margin: 0; padding: 0; background: #000; overflow: hidden;
}
canvas {
  position: absolute; top: 50%; left: 50%;
  transform: translate(-50%, -50%);
  max-width: 90vw; max-height: 90vh;
}
#imageCanvas { cursor: grab; }
#imageCanvas:active { cursor: grabbing; }
#codeCanvas, #overlayCanvas { pointer-events: none; }