Pretty fun game and a cool theme. the pixel art was very cute. I really liked the bank shot mechanic and I like that the ammo is almost like a second health bar since you need to gamble to get more ammo.
As for things to improve, i think having more sound design would help the feel and feedback of the game a lot. Even keeping it simple, having more sounds trigger for different things will just make everything feel more responsive.
Also personally i felt like the fixed fullscreen camera was a bit too wide and made the game feel a bit small, perhaps a following camera would have felt a bit better.
Overall great job, I had fun with it :)