This is a really good entry. I liked the hectic bullet patterns of the bosses, where they would start off pretty easy, and get challenging real fast. I think my favorite was the 4th boss, I really liked the push/pull mechanics, and I think it used them very well. I also really love the final boss and how it kind of ties back with the main mechanics of the game. I think the gun-making and mashing space rapidly to get as much damage in as possible is satisfying, but I do think it could be made even more satisfying. For example, if the player became invincible and had bullets bounce off of them while they have the gun, maybe even a music change. I also think it'd be nice if the scraps would spawn instantly after you pick one up, (although you'd have to give the bosses more health), so there's less waiting around and more go-pick-that-thing-up action. But, those are just some small things I noticed. Great work!