This game is genuinely great. The art is solid, the gameplay is tight, and the music is good. It's a puzzle platformer, challenging, but I never found myself calling ♥♥♥♥♥♥♥♥ on any of the levels. The only trick is to know when to upgrade and then come back to a room.
The guy who made this deserves your money. It's worth the off-sale price, but if you must, buy it on sale. If you like this sort of thing at all, get this game.