Great job on the game! I just beat it, though I didn't do the invisible mode or fewest number of moves. I love pretty much everything about this game, though I strongly recommend adding an undo button. It really helps to take the frustration out of difficult puzzle games and I think it would be especially beneficial on the last two levels. I would also recommend adding the arrow keys as an option for movement, as some people prefer it or have AZERTY keyboards that make WASD movement very inconvenient. Lastly, to help with accessibility, it would be preferable to export the game as a single executable rather than an installer.