I utterly suck at this game - but it's so good I keep coming back to it.
This gives me the same kind of vibes as Ultrakill, but 2d - enemies are quick, and unforgiving. It's tough - but when you come out on top, you feel like you achieved something. Learning their skills, their patterns, and reacting accordingly. The sound design is pretty well put together, and the art aesthetic and style is also really well put together and cohesive.
I think the core loop could do with some polish only with the damage you take - I found myself a little unsure if I had taken harm, but that could also just be a skill issue on my end.
The ending was fun - I was down to the wire, as was the boss, and I pulled the trigger at the same time they did. Returning to the main menu left me wondering if I'd won or lost - which while a proper win or lose screen of some kind would be cool, almost felt a little poetic.
This is a really solid proof of concept - you could make a cool deckbuilding style roguelike out of this, maybe with extra bullet types and upgrades to go alongside?