Thanks for the review!
The game still has various problems performance-wise, which is why it slows down when there's more than one enemy on screen.
The player blinks when hit by an enemy, but has infinite health.
The boss is very much unfinished, which is why it glitches.
The power-up system is heavily inspired by Gunstar Heroes, meaning that you can have up to two weapons at the same time, and can press a button to alternate between using just one of them, either the primary or the secondary, or you can use both at the same time, which results in a weapons that combines both of them.