A game in which you control a little white square which has to reach the littler grey one. Each time it does that, however, a new little white circle appears moving horizontally or vertically, and if our little white square touches one of those the game is over. And that is a Bad Thing.
Sizer mode is the same, but you get bigger each time you get a circle. Survival mode is basically the reverse of normal: your score is in seconds (each second or so an obstacle is created) and each time you get the target one of the obstacles goes away. Two Player mode is cooperative, trying to score as many points together as possible. Two Player VS mode is, inevitably, antagonistic and each must get a higher score than the other.