Very interesting game and very interesting idea to control that blue orb to absobe bullets, I liked a lot. However the lack of any GUI that gives feedbacks to the player about, i.e, how long will it take to spawn the boss, how much is charged the blue orb, etc. made me feel lost (I thought that it was an infinite autoscroller when suddenly the boss appeared), so, according to me, it's a must to add.
I think also that the collision between the orb and the spaceship can be kinda too punitive and it's really frustrating when you get slowed down because of it.
I liked the particle effects and light effects, but I agree with those who say that the background make game assets hard to distinguish clearly.
To sum up, well done, it's a very nice game!