1) The puzzles were pretty easy, the last one had me a bit confused for a few moments, but a bit of moving around helped me figure it out.
2)No bugs.
3)Not most of the times, but the logic of the last one didn't quite make sense to me. Maybe i didn't understand it, feel free to explain.
4) The art fit the theme of the game pretty well. Clean visuals suit puzzle games. :)