Agree with all the comments - great core mechanic and awesome you were able to get three puzzles done in the time we had! You could easily expand this to more puzzles if you have that interest.
I saw on the game page you mentioned wanting to add enemies, that would be interesting.
I think you could make a minor tweak of adding a way to rotate the pieces the opposite direction and just some minor sound effect when you rotate a piece might be nice and add a lot for little effort.