For a solo project in four days this is pretty good! Everything from the gameplay to visual style is very retro, and gives me very new-era boomer shooter vibes. I like what this game is putting down, and the end result is surprisingly in depth for such a short span of time.
The sound design and enemy responsiveness could do with a bit of work, but it's pretty good as is, and serves as a really solid prototype. My only critique was the shotgun being a single projectile - it might've made more sense as a silver bullet revolver or something? - but that's a real nitpick.
All in all - really fun shooter! Nice work.