Very satisfying to play. Enjoyed myself.
The art is cute, the red and gold enemies look very majestic somehow. The music strikes a good balance between happy and energetic. The take on the theme is effective, and the leveling up is interesting enough that I didn't need any other reason to play the game for quite some time!
I read somewhere that you were thinking of releasing a post-jam version, so I thought I'd place my thoughts more articulately. Stuff that I think could use some polish: the character controller - as another comment mentioned, the jump gets pretty clunky especially the larger you grow. Since the combat mechanic is simplistic, having clean movement would make it fun. I found myself trying to hunt larger slimes specifically to get large level boosts, and a large part of that was to time jumps/dodges. I also think the spaces on the playable area where Slimer couldn't go once it leveled up a bit(because thicc) were a bit difficult to make out. If it could fit through some of the stuff that it looked like it could, that would be cooler (like a little forgiveness mechanic on the movement). And about the level up part - it wasn't very clear how much I was growing in each levels, so sometimes it felt unsatisfying.
Cheers!