Odd-Y

Odd-Y is a connection game played on a hexagonal grid containing an odd number of sides of equal length (thus, an equilateral triangular board, or an equilateral pentagonal board, or an equilateral heptagonal board, etc.).



RulesOn each turn a player plays a single stone to an empty cell on the board; once placed, stones do not move. Corner cells belong to both of the sides that they join.

The Pie Rule applies: after the first stone is placed on the board, the second player can choose either to play a stone of his/her color, or swap colors with the first player.

A player wins by connecting a set of three sides of which the following is true: a triangle drawn of straight lines connecting the mid-points of each of the three sides contains the gameboard's midpoint (i.e., has the gameboard's midpoint inside its borders).

Draws are impossible in Odd-Y. For each way of completely filling an Odd-Y board with stones, there will always be one -- and only one -- winning group of stones.



CommentsWhen played on a triangular board, Odd-Y is also known as 3-Y. Likewise: 5-Y on a pentagonal board, 7-Y on a heptagonal board, etc. Note too that 3-Y is equivalent to The Game of Y designed by Ea Ea. Thus, Odd-Y is a generalization of The Game of Y. Ea Ea himself discovered 5-Y on a pentagonal board, which he called "Star Y" (stating the win condition as one wins by connecting three sides, not all of which are adjacent). Odd-Y generalizes 3-Y and 5-Y further, to any hexagonal grid board with an odd numbered of sides.