Really nice job!
The level of details, the art style, everything is on really proffesional level.
I like that its a true boss rush.
I like the boss design, where we are punishing self and the boss only provoke to it. Its really lovely trick.
The main issue its with the pacing, where sometimes we have to wait for example 10 second without possibility to do anything. Phases where we should focus on dodge and survive could be fun, but over all in your boss design, we can simply spend this time in safe spot. So much time we got punished for take a effort, such as when we go through the waves of projectiles to move to the eye on the opposite site of the boss, only to shows that the boss close this eye without taking any hit.
Over all my score is really high, and GJ!