Very charming Castlevania-style platformer. The only real flaws were the slowdown and low difficulty, but those are both adressed in the Color version, so joke's on me for playing this one first.
It's a bit on the short side, but not at all exceptionally so by Game Boy standards. The parallax scrolling on many levels was most impressive!
Overall, very well-made and fully-featured---and even more so for a game jam game!