Everybody else said the same thing, the art and the music are excellent, kudos to the respective artists.
Maybe I haven't played the game long enough, but it seems that having several bubbles only makes you complete the same level a bunch of times, and it really doesn't benefit from what could be a sorta "coop" experience. (Again, I haven't played that much of the game but it's the feel I got from the first levels, so if I am mistaken I apologize!)
I think it could be cool that bubbles could collide with components such as levers and other bubbles to give it some sort of "puzzle" feeling, not too much so it's professor Layton, but just a little bit so that the game keeps fresh the entire time.
Overall, good job!