This is way better than some other 'amateur' games that I have come upon. I can imagine it being used fairly well in a virtual pet site or social/mini game site. Of course, improvement never hurts. I would like your leveling system highlighted more. I realize that you have released bubbles at a quicker rate as you advance, but the fact that there is no losing means that you can fail at the game and still in two minutes be in the max level of a bubble a second. I think adding in a limit of how many you bubbles you can lose (you can even add extra lives as an 'upgrade') would be very beneficial to the longevity of the game.
This is a fantastic start! If you keep working at this, you have many more games in your future. ^_^