This is a very good puzzle game indeed! Good puzzle games in jams are always a rarity and it always makes me happy when I see one, let alone one with fairly unique mechanics! The difficulty was just right for me as a puzzle game lover, and I think that undoing blocks was a very interesting design. It certainly feels like there is potential to be elaborated much further. Well done!
For some feedback, I like the simplistic art style very much, but especially for the first level, this isometric view without any shadows makes it very hard to determine how the map looks like with any elevation. I personally think the visuals of a good puzzle game should always be in service to the understanding of the puzzle regardless of art style, so I guess there should be some adjustments. Ideas such as different colours for different layers, shadows, harder edges etc would be a nice touch. I will also suggest adding a few more colours for the movable block. It's now all purple, and when two of them are on the same level, it's not trivial to tell apart which is which.
Anyway, I think this is a very good puzzle game! Well done!