Great, Frustrating
I loved this game when I was linked to it on your site a couple months ago, and I still love it now. It's one of the rare games that manages to have smooth, almost-flawless gameplay, and maintain an outstanding look, sound and feel.
My only problem is that, while the score system encourages you to collect the bubbles, the level framework discourages you to do so. I can't tell you how many times I've missed a bubble, accidentally slid out of the level, and had to restart the ENTIRE GAME, simply because I'm not allowed to go back a level. Since you added mid-level checkpoints, it makes the problem worse! I think by now I could easily get 100% bubbles, if there were a "jump to level" button (or even an option to replay the recently completed level instead of continuing). I don't think I'll ever have the patience to get 100% in one try with absolutely no mistakes.