It was hard, but one of the more visually appealing bosses I have played. Nice job.

Thanks! Was it too hard? Did it feel impossible or could you feel victory nearby?

well some of it's attacks are impossible to dodge, you could slow the bullets a bit so it wasn't that hard.
also, since you HAVE to take the blaster to damage him, why not give it to the player when he enters the room?
one more thing, when the boss gets enought damage and starts a second animation, that's when everything goes impossible, he is too quick to aim so are his bullets to dodge, if it needs to be that fast then you could either give the player a shelter where neither him or the monster can attack each other or decrease how often those bullets are shooted, making it possible to dodge, it is however, essencial that the boss stands still after some times running in that velocity, giving the player time to react.

I think this makes me clear, I hope it was helpful.

@Kling
Thanks for the feedback! It'll be very helpful indeed. Just as an added note though, it's not required that you use the blaster so much that it just makes it go a lot faster. I might put the blaster in a harder to reach area. Also, I'll make the floor be less flat. The room itself will also be considerably smaller in the final version, because I just put the boss there before finishing up the "fire" part of the level.