Cool game. The graphics are very well-made for a game jam, and it looks more professional than most entries.
The game's visual profile and contrast seem in a pretty decent shape overall, with a few issues. In particular, the black/dark gray bullets are way too hard to see. I'd also like to see more visual communication of the enemy mechanics, since most of them aren't super obvious without taking the time to observe them closely.
The black hole mechanic is a cool idea and it plays all right, but I think it could be much better. The fact that bullets all the way on the opposite side of the arena seem to accelerate at about the same rate as those very close to the black hole feels very strange to me, and it's frustrating to have my bullets pulled so hard (making it harder to aim) even when a black hole is very far away. I'm also skeptical of the design pattern of giving the player such a powerful tool and then having some enemies that take it away--perhaps simply making them a more limited resource in the first place would be a better approach?
Smaller things:
It would be nice if the game paused while the controls were being displayed, or if you could display the controls while in the main menu. I was in a rush when I looked at them the first time, and missed, among other things, the fact that you can zoom out.
On that note, I'd recommend setting the default zoom level further back. It's quite hard to learn the enemies' mechanics when they're off-screen, which happens a lot unless you zoom out manually. I found the game much more confusing before I figured this out.