The polish on the visuals, transitions, splash screen, tutorial, etc, feel really professional!
I'll admit, the third level got me. I tried activating the tricky tile from the correct ground level, but it didn't work, so I gave up. I eventually tried the game again once reading other hints, and found that I could access it from the back left side, but I don't understand why it should only work from the back left and not the front left or front right adjacent squares.
Still, very impressive to have such a polished-feeling game with multiple levels done in such a short time!