I wasn't sold on the first boss, but after that it felt really better. It's instant fun and most of the game mecanics felt right, except for crafting the ammo, I'm not sure about having only one place to throw the parts being at a corner instead of being in the middle.
The story is a nice addition, but felt like long text, maybe it could have been sold better (like maybe having the character say things himself with dialog boxes after each fight? I don't know). Boss 3 is definitely challenging, a bit unfair even with having both minions AND bombs at the very beginning of the fight. I had a good time though!