Really good concept here and a damn good execution of that concept
The presentation as a whole is also damn cool, however I felt like the readablity of some of the levels wasn't as good as it could have been. There are some levels where the colour of the enemy bullets contrast with everything else and you can see them properly, whereas there are certain levels where the bullets are just a different shade of the background colour and kinda caught me off guard at some points.
I think the best thing about this game is just how you took this concept and ran with it. Simplicity and versatility in mechanics at their absolute best. The variety present added more, but didn't really change the fundamentals any more than it needed to
That said, I'm not really a fan of level 15. I'm guessing the idea was that the second bullet becomes a projectile, but it felt more random than anything else to the point that all of my deaths in that level felt pretty random and unfair. Especially since I felt like the levels prior to this were balanced pretty well imo ( Or it's probably just a skill issue on my end lmao )
Unfortunately I didn't manage to get past that level lol, but everything I played till then was damn good. Great job on this