The game has nice clean graphics, and playing it was a fun, smooth experience! I like the unique concept.
The puzzles were difficult for me, so I wasn't able to unlock World 4 to see what mechanic was next. I think having a 'skip' button would be nice for when I cannot figure out how to solve a particular level. Also, I think it would be good to have the controls in the description as well. I didn't realize that 'P' was the key for the pause menu.
Otherwise, it was great, I enjoyed it!