Not ready for prime time
Interesting idea, but there's a lot of polishing to be done. I feel that around the time the game starts to require some interaction is also about the same time when you get sealed in the corner waiting for your death, temple of doom style. I feel the graphics were a bit plain, and even a simple music loop could have added a lot of warmth to the game experience.
Here are some changes I would like to see-
1) add some background art that changes upon level up
2) sleeker graphics for the bubbles, perhaps something with a little transparency
This would be more difficult, but making the green boundary box a different shape, such as an irregular polygon or (better still) a maze would add a lot more interest. Or alternately, having the bubbles be actual enemies with AI and blasters would add a lot more interaction and a lot more fun. Another thing you might try would be to include a weapon or powerup that you can use to fragment and scatter the bubbles. Just some ideas to mull over.
I think the general idea is interesting, and the play control itself is pretty smooth, but I think it needs better packaging to become a more complete gaming experience.
Don't get discouraged! I think you're heading in the right direction! I look forward to seeing more of your work!