This game is incredibly cathartic to play. The look and feel of the physics is spot on!
I feel like the game could use some kind of cross-hair. Even though the bullets are projectiles rather than hitscan I feel a crosshair would at least help you line up distant shots.
The kick hitbox felt really inconsistent. When it connected it felt fantastic but there were a number of occasions where i felt like the kick should have landed but it didn't and also the opposite.
Other than that, the game does lack a little variety. Perhaps different enemy types with their own mechanics might help, or some power ups that spawn around the arena? There's also nothing really discouraging me from just kiting the silly boys around the arena for 5 minutes just to clear the stage. This paragraph is mostly suggestions really, I have no idea what might improve the game or clash with its current design, to be honest.