Aside from the massive spikes in difficulty, it's pretty good.
Speaking of difficulty spikes, level 17 seems to be impassible, like, to the point where I'd actually say the game is glitching out. I've tried every combination I can think of, from the most straight forward to the most absurd, and still there is always a piece off. I've starred at the screen so long it's giving me a bloody headache while I blazed through all the other levels of the damn game. I've even sunk to looking up a walkthrough, of which there is absolutely none, which makes me yet more suspicious that it's simply designed improperly.
If anyone can prove this is some type of mis-matched program indeed, I'd appreciate it; as the only other option is that I'm a knuckle dragging retard who can't see the solution in front of his face.