This is quite a solid roguelite shooter, I'm surprised there aren't any comments.
Nice retro graphics, sounds, music, story, fun mechanics, mostly balanced upgrades, a menu! It definitely has a polished feel overall.
The only upgrade I felt was lacking was the shot AoE + CD, Long Fuse, was it? AFAICT, the explosive enemy one is pretty much the same without its drawback, but I could be wrong.
Take this with a pinch of salt as I'm in no way a designer, but I wonder if some visible cue to the game's genre might help catch people's eye. I could tell it was likely a high quality one just by the cover, though.