You've got a nice idea here and the art looks lovely, but some elements of the design don't quite make sense.
For example, you can shoot mulitple bubbles at once, which is really fun! BUT, there isn't much incentive to do that. It makes it harder to keep the bubbles in the air, but you don't really gain anything in return.
I think the power ups could do with being a little clearer. I was avoiding all of them until I accidentally hit one. Then I proceeded to aim for "the red power up" and was disappointed to discover that the reward for that one was death. Perhaps the red one could be triangular? Or some other non-circular shape? The power-ups would benifit from the addition of sparkles or or something. Anything to make them look like something you want to interact with.
You have a very interesting idea here. You just need some tweaks to really bring it together.