Wow what a game! I loved everything from the effects you get from each enemy kill to the overall physics of the gunnerang. There's really nothing I can criticize about this work. It's addictive, fun, fast paced but never too too overwhelming.
If anything (I know this is just a nitpick) but the gun bullets feel a bit too random to count towards just killing enemies. It's rewarding to get a kill like that but I don't really feel like I'm the one that landed that hit if you get what I'm saying. A cool addition would be that the bullets also damage you, so you have to be weary of their trajectory as well maybe (? unless it's too fast for the player to react in time. It's worth trying it out anyways!). Alternatively you can also control when the gun fires, the lack of control comes from how hard it is to time the bullets getting fired (and you being unable to just spam it lol).
Those are just some of my ideas of how you could expand an already phenomenal game. It's really up to you if you want to take any of those tips! The randomness of the bullets firing didn't take anything away from my experience I'm just postulating how you could add even more to it!
Anyways I'm rambling for too long, great work you two! This really is something else :)