You have to place the magnetic balls in the pits on top of the nine dice. There are two variations of the game.
One is to place the balls tighter than your opponent. It's mostly a solitary competition.
The second one is more strategic. You roll all nine dice and have to announce how much of the pits you can fill. Than the next player places the dice in the box. Than every player places as much balls as he wants (and is able to) on top. At last you have to place your announced number of balls or more to get points. If you don't succeed you get the negative of what the other players could overcome your announcement.