Wowowowow! Binding of Isaac on Gameboy, what an absolute delight! This is a such a wonderful treat. The only nit pick I *had* is when I first played, I was getting frustrated with the control of shooting the tears being so tricky. But then I read the one line in your instructions where you said you could hold down the fire button to lock in your aiming direction. Once I figured that out, this game played wonderfully mechanic wise.
Building this in C too, AND it can be ran on GB Hardward?? Kuddos to you; really really awesome. I'd love to see you build upon this; music, sounds, varying enemies, bosses, etc. I believe you could do this justice just from the framework you've built for this jam. I really hope to see more come from this, I'd definitely come back and play more!!
Outstanding job!!