Cool! Thought I’d hate it at first, but it’s fun and rewarding. The music is fitting, although the beat started to annoy me after some time. I liked the variety in enemy balls and their effects, which also were visually pleasing and in sync with the mellow and spacey music (again: the beat is unfortunate).
Downsides: it never really gets hard. It’s easy to implement a little strategy: not picking up stars too fast and biding your time until most balls destroy each other make most levels very easy, especially with high health regeneration. This is a little risky when a large amount of big balls is involved, but that happened to me only once. I think a countdown timer or time penalty could be a great way to force the player to combine strategy with risk-taking. This would require a bit more skill and make the game a little harder, and this is just what it needs, because the upgrades, though welcomed, are easy to receive and you’re never really dying for one as the upgrades continuously keep you too strong or efficient to be bothered much by the enemy balls.
Also, I didn’t see a point in the water resistance upgrade. I don’t think that ever affected me.
All in all: cool and highly enjoyable game, but a tad too easy and too short.