First of all, really fun game, and looks great too.
I see others have already mentioned this, but the axe collisions are really frustrating. I felt like I couldn't use the jump ability, because every time I thought I'd cleared a path, it turned out that the axe had missed by a pixel and I jumped straight into an enemy.
I love the squash and stretch as the character lands on a wall. Also, the way the level transitions to the shop.
The enemy design is very clever. The lizards, in particular, support the main mechanics really well.
PS. I know the definition is ridiculously broad now, but I don't think it's reasonable to call this a roguelike. The levels are the same every time you play. Just a pet peeve.