Really like the music, and how it fluctuated a little between rooms. I'm not normally a score-attack kind-a guy, but it really works here, and the variety in what could be in a given room only drove me to explore more. Same thing with the different enemies, looks like smartmagpie said they preferred the Mushroom -> not me, I liked getting the laser eye.
Over all, great work, a blast to play!
(I'll probably hit it up again. It also feels like something you could keep adding to, something special about your color choices, and the tilework feels otherworldly)