I'm liking the game so far but I'm also biased towards rogue-likes. If I were to make a suggestion, it would be to remember that rogue-likes work best when they have synergies and disadvantages.
For instance, an upgrade to fire breath that sets enemies on fire could synergize with poison breath to create an explosive effect. Or maybe add throwable vial of oil that makes eating enemies faster, but ignites when set on fire. Either way, the player could ignite themselves via enemy explosion or from contact with an inflamed enemy. But this is just a suggestion, you don't have to take it seriously.
I also ran into a bug that soft-locked the game.
Bug in 0.51: I'm stuck in an infinite floating animation. This occurred after beating a elite enemy room and picking a max health upgrade from Span. I think I left while the animation was still playing because I went to the next room (egg room) and a second upgrade menu appeared. I was still in the floating animation and selecting another upgrade didn't close the did nothing. The game seemed to be stuck in a loop as it did accept my second selection, but didn't move from there.
I hope this helps, keep up the good work.