Hundreds

A really simple concept drives this game. A few bubbles run around the screen, and you have to touch them in order to inflate. As log as you touch a bubble its value increases. The goal is a cumulative score of 100 for all bubbles on screen. As usual with these games it starts off easily but after a few levels it gets really tricky. There's a paid iOS version out there, but I suppose most people will settle for the free version, right? :)