I love all the games you've put up from prototyprally, they're very original and fun. This game is simple and addictive, and entirely original. Good job!
By momentum do you mean like having the person you're controlling not respond quicckly, like inertia? The collision detection by the way, is HitTest, i tried making the hit testing work better (i.e. only respoding when you actually hit the other bubble), but it wasn't as satifying. For those of you who thinks it's too hard i'll try to put in some leveling, like choose your game mode - easy med. hard.
 "fungus"){kind=icon}
 "eleminer"){kind=icon}
 "Pretty Pretty Bang Bang"){kind=icon}
 "Gamma Bros"){kind=tracking}
 "HoverBot 2"){kind=icon}
 "Silhouette"){kind=icon}
 "Balloon Go Pop!"){kind=icon}
 "The Bubble Game"){kind=icon}