Hmmmm... if my intel is correct, this is a Super Meat Boy clone for the Virtual Boy xD. Anyways, I think you should maybe add more enemies, 'cus the gun is useless for the first part.
When you think your playing a platformer, but then there's Goombas and Koopas so you think it's Mario but then they're not Goombas and Koopas and your like WTF.
Hey, I also have a few things to say. First, AWESOME game. I've been looking for a good browser Hack 'n Slash, and found this.
Suggestions:
1. They're already good, but if you could, maybe once in a while add some new enemies and items.
2. Maybe you could a Mario Maker-type level editor to make your own levels? IDK but I think (from the perspective of someone who only uses Scratch) that could be pretty easy? Anyways,
3. Final suggestion: ADD BIOMES!!! I can't stress. this enough, the grassy terrain gets boring and repetitive, and there is no real sign of progression. That's all from me, and I still love the game. Fav + Playlisted.