That was fun! I spent much more time playing this game than I thought I would. If I had one complaint, it's that you made the enemies too adorable to shoot at.
Seriously though, I think this is a pretty solid concept, and the corruption mechanic does make the game more interesting. I would suggest forcing the player a bit more to become corrupted, because I managed to get pretty far into my last run without taking a single corrupt heart, so I just got too powerful for the enemies to keep up.
All in all, very solid work!