The art in this was cute and appealing! Leaning into the slime theme for the strange matter would be neat!
Even with the description, shooting the same things that can kill you was a bit confusing and I never figured out what the orbiting sword is for. Having enemies that try to stop you and make you risk cluttering up the play area with strange matter might be good as otherwise it made more sense to only shoot when on top of a planet.
I think there is a lot of potential here, especially with the idea of the balls growing bigger and harder to avoid, like a difficulty slider. A hard edge to the map or teleporting you to the opposite edge might be better than going off screen. Once I got into the swing of things it was fun -the momentum meant you could just about dodge out of the way of the matter balls if you are quick about it. Overall, I had fun with this -cool stuff and good work!