I like that the base of the game is simple (avoid and hit) while aesthetics are eye candy, so the game is aesthetically overwhelming but easy to use; the other way around would be a complete disaster but this way you have the foundation for an incremental arcade. At first I thought that I could break the balls, and I wondered if the enemy would use different patterns of attack; this could be added in further versions.
What I think that can be improved is the feedback on the state of the game (I had no idea there were phases) and not hearing when you are hurt or the bullets made me feel a bit lost. The idea of the tiles floating looks very cool, although it would be better if the space you see could be directly associated with pain (as if you saw lava, you would immediately think that will hurt you a lot).
Great visual experience!