Some of these puzzles felt a bit too simple, almost filler-y, but disregarding those there were plenty of good ones, and I appreciate that you didn't use the undo wildcard as an excuse to make a bunch of levels where one wrong move means you have to reset :] The plot was simple but well told and tied into the mechanics (and there was one in the first place) so well done there.
One complaint I have to make though - there's nothing wrong with tile based movement, but requiring a keypress per step isn't great even if the last few levels in your game aren't just a long, straight, hallway. Other than the contribution to the erasure of the label of my keyboard's D key though, I've enjoyed my time with this game.