Took some time to digest the mechanics, but once I did, it was a lot of fun! Love the simplicity of the controls contrasted with the complexity of info you need to digest to make the right decision of when to swap vs not.
Loved the sound and graphics, and very impressed with all the info you managed to squeeze into the resolution.
Found it really unintuitive to hold to swap weapons with the current implementation. I think it'd be better if holding for ~500ms triggered the weapons swap immediately, rather than having to release. Also having the swap sound effect play repeatedly while I held the button, despite nothing happening is confusing.
It'd be good to refine the early RNG a bit. You probably shouldn't get shops until at least turn 30. You should probably guarantee a weapon within the first few encounters.
Overall an excellent submission, well done!