Cordon

Cordon is a two-player game played on a hexagonal grid of any size, initially empty. The two players, Red and Blue, take turns placing their own stones onto unoccupied cells of the board, one stone per turn, starting with Red. To cordon off cells, extend a path of stones between (and occupying) two perimeter cells. Consider the shortest perimeter path between the two perimeter stones. The cordoned area is comprised of the stone path, the perimeter path, the cells (occupied or unoccupied) that they surround, as well as all stones in a group the stone path may be part of. If you have formed a stone path that includes two perimeter stones directly opposite each other on the board, you have formed two shortest perimeter paths and cordoned off the entire board. A cordon is nullified and rendered irrelevant when it has been surrounded by or included within an enemy cordon. The object is to cordon off more cells than your opponent.