But that is not all. The thing that makes this app different from the other math apps is the social aspect. The author who goes by the name of TwZ added achievments, leaderboards and even an option to challenge real players, including your friends from contact list.
Without the social part, this game would probably be boring as math can be sometimes. But the option to compare yourself to the world and especially to your friends keeps you engaged.
If you are a competetive person, you will probably find yourself coming back to this game. And in the meantime you will practice your brain which is never a bad idea.