Pex
Overview

Pex is a two-player abstract board game played on a board with pentagonal tiling that was invented by David Bush, an avid Hex player. This game is a member of the connection game family including such game as Hex, Y, Atoll and Crossway.

The pentagonal tiling was taken from the list of 14 known tilings of congruent convex pentagons.  Two criteria had to be satisfied:

  1. Nowhere should more than three edges meet at any vertex.
  2. The tessellation should be topologically distinct from a hexagonal grid.  In other words, not all the interior cells should be adjacent to six other cells.
The only patterns which met both criteria were patterns 11 and 14.  In pattern 11, half the interior cells are adjacent to seven neighbors.  These are colored yellow.  The other interior cells are adjacent to only five neighbors, and are colored green.  Pattern 11 was chosen because the playing grid seemed more inherently fair; in other words, the task of connecting the blue borders seemed about as difficult as connecting the red borders.  With the pie rule in place, a fair game was virtually guaranteed.

This tesselation was discovered by Marjorie Rice, who deserves equal credit in the creation of Pex.

Objective
The objective of Pex is to create a connected chain of a player's pieces linking the opposite edges of the board marked by the player's color.

Board

Pex is played on a special board with pentagonal tiling.  Pairs of opposite board edges are marked with two colors, usually Red and Blue.

Play

The game begins with an empty board.

Each player has an allocated color, usually Red and Blue.

Players take turns placing a stone of their color on any empty cell of the board.

Since the first player has a distinct advantage, the pie rule is generally used for making the game fair.  This rule allows the second player to switch colors as his first move.

End of Game

The game ends when one of the players forms a connected chain of his stones linking two opposite board edges marked with his color.

No draws are possible in Pex.

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