(PS: Now that I've finished the game, I noticed that the level select references bonuses, is there something special you have to do to reach these levels?)
I know you're not implementing undo and totally respect that. But for what it's worth, one reason undo makes puzzles more fun is that doing this accidentally is no big deal instead of making me want to give up for the day:
Yeah, I'm aware there will always be happening things like that without undo. The reason I won't include such a function is because a lot of players will actually bruteforce the levels by undo-ing every tiny move instead of thinking a bit ahead. I know it's not a perfect solution, and I guess you made a point with this level since it's easy to trap yourself in the borders, it's not perfectly designed.
The bonus level should be playable by clicking on them on the level selection menu (that you can access from the main menu), there's 4 of them and all 4 should be accessible to you.
Also, thanks for playing and congrats on finishing the game :D
