1. Quadrant Hex is a game for two players, Black and White, who alternately put stones of their color on the board. Once placed, stones do not move.
2. The board is a 10x10 rhombus divided into 5x5 quadrants, as shown in Diagram 1. At the beginning the board is empty, and play takes place on the cells.
Diagram 1 --- the board for playing quadrant Hex
3. A corner cell, whether of the full board or a quadrant, is considered to belong to both edges that meet there.
4. It is permissible to pass.
5. It is not permissible to "mirror" the opponent's moves ten or more turns in succession.
6. The beginning of the game is governed by a "refined" pie rule. Player 1 plays two moves for Black and one move for White. Player 2 then decides which side to take, with White to move. Note that the standard pie rule is encapsulated within the refined rule, because it is permissible to pass a turn. (I.e., Player 1 could play one move for Black, then pass for White, then pass for Black.)
7. Five games occur simultaneously --- one on the 10x10 board and one in each 5x5 quadrant. The object is to win at least three of them. In each game Black is trying to connect the upper right to the lower left, and White is trying to connect the upper left to the lower right. In Diagram 2 White has scored one point, winning the large game by connecting the upper left edge (at C10) to the lower right edge (at J1) --- note that J1 is considered to belong to both the upper right and lower right edges. White has not yet won any of the small games.
Diagram 2 --- White scores one point
In Diagram 3 Black has scored two points. He has won the upper quadrant game by connecting its upper right (at J8) to its lower left (at F6) --- note that F6 belongs to both the lower left and lower right edges of the quadrant. And he has won the left quadrant game by connecting its upper right (at E9) to its lower left (at A7). The large game, the right quadrant game, and the lower quadrant game are all up for grabs.
Diagram 3 --- Black scores two points
In Diagram 4 Black has won by a score of 3 to 2. He has won the upper quadrant, the left quadrant, and the lower quadrant. White has won the right quadrant and the 10x10 game.
Diagram 4 --- Black wins, 3-2
Quadrant Hex can be conveniently played with pen-and-paper. Just mark an open circle for White and a closed circle for Black. Diagram 5 shows an example of a completed pen-and-paper game. White has scored the necessary three points to win. (The left quadrant, the upper quadrant, and the 10x10 board all belong to him.)
Diagram 5 --- a completed pen-and-paper game