Cool game idea! There's a ton of potential in the "rewind level" concept here, though I wish there were more restrictions on the player. For instance, whenever you're stuck, it's easy to "cheese" the level by just scrolling through the previous levels one by one to find out the right answer, so even without hints the game is quite easy. Some kind of punishment/drawback for rewinding might help give the game higher stakes, and keep it interesting.