Quoridor is played on a game board of 81 square spaces. Each player is represented by a pawn which begins at the center space of one edge of the board. The objective is to be the first player to move their pawn to any space on the opposite side of the gameboard from which it begins. The distinguishing characteristic of Quoridor is its twenty walls. Walls are flat two-space-wide pieces which can be placed in the groove that runs between the spaces. Walls block the path of all pawns, which must go around them. The walls are divided equally among the players at the start of the game, and once placed, cannot be moved or removed. On a turn, a player may either move their pawn, or, if possible, place a wall. Pawns can be moved to any space at a right angle. If adjacent to another pawn, the pawn may jump over that pawn. If an adjacent pawn has a third pawn or a wall on the other side of it, the player may move to either space that is immediately adjacent to the first pawn. Multiple pawns may not be jumped. Walls may not be jumped, including when moving laterally due to a pawn or wall being behind a jumped pawn. Walls can be placed directly between two spaces, in any groove not already occupied by a wall. However, a wall may not be placed which cuts off the only remaining path of any pawn to the side of the board it must reach.
History
Quoridor is also based on an earlier game invented by Philip Slater, Blockade, in 1975. Marchesi also created another version of this game, called Pinko Pallino, which was published in 1995 by Epta. Pinko Pallino was only for two players and was played on an 11×11 game board with a total of 42 walls and slightly different rules.
Notation
Although there is no official notation, Lisa Glendenning's thesis proposes a reasonable notation. The notation proposed is similar to algebraic chess notation. Each square gets a unique letter-number designation. Columns are labeled a through i from player 1's left and rows are numbered 1 through 9 from player 2's side to player 1's side. A move is recorded as the column followed by the row as in e8. Player 1's pawn starts on e9 and player 2's pawn starts on e1. Each pawn move is defined by the new square occupied by the pawn. For example, if player 1 moves from square e9 to e8, player 1’s move is e8. Each fence move is defined by the square directly to the northwest of the wall center from player 1's perspective, as well as an orientation designation. For example: a vertical wall between columns e and f and spanning rows 3 and 4 would be given the designation e3v. Games are notated as they are in chess: by the move number, player 1's move, and player 2's move. For example, a game might start with each player moving their pawn towards the goal: 1. e8 e2 2. e7 e3 And then the players might add walls to lengthen the other player's path: 3. e3h e6h and so forth.
Strategies
Reed opening: This opening consists in placing, during the first two moves of the game, two walls on the third row in front of the opponent with a single gap in the middle. This opening is attributed to Dr. Scott Reed, a known military strategist and frequent player. A counter-strategy to the Reed opening is to place two horizontal walls on the third row, one at the extreme left and one at the extreme right, which effectively reduces both players' path counts to one. The game would start as follows: 1. c3h a3h 2. f3h h3h
Shiller opening: Both players advance their pawns three times. This opening is attributed to Larry Shiller, who is also known as the Voice of Backgammon. Then the first player places one wall vertically in the column closest to him, providing two paths for the other player while maintaining just one path for herself. The Shiller opening implements the strategy of maximizing the opponent's path count and of minimizing one's own path count.
