4 Way Puzzle: you start with a black dot in the center and must build on it from the bottom, then the left, the top and the right. When a cluster of one color occurs, you score points.
I'm not sure exactly how the scoring works, but larger clusters score a lot more points. Also, if you've got a red piece on top of your emerging blue cluster, when that blue cluster is finally formed, it will disappear as well as that lone red piece.
The game ends when you cannot make a move.
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