Othello (Reversi)

Reversi (more recently also known as Othello) is a two-player board game that was invented around 1880 by two Englishmen, Lewis Waterman and John W. Mollett.


Reversi is played on an 8x8 board using special two-colored discs: one side of a disc is colored black and the other side is colored white.

There are two players: White and Black.

The initial position of the discs is shown in the following picture:



The goal of Reversi is to occupy more board cells with your own discs than your opponent when there are no more legal moves available, usually a result of the board being completely filled with discs.

If the game ends with the same number of black and white discs placed on the board then the game ends in a draw.


Players move alternately, starting with the player controlling the black discs.

Each move consists of placing a single disc of a player's color to any empty cell of the board that results in flipping at least one disc.

After placing the disc, a player flips all discs of the opponent's color lying on a straight horizontal, vertical or diagonal line between the newly placed disc and other discs of the player's color already placed on the board.  Important notice: the opponent's discs are flipped if and only if there are no gaps (empty cells) between the newly placed disc and other player's discs.

 Below are several examples

If the black disc is placed in the specified cell then four white discs in three directions are flipped.


If the black disc is placed in the specified cell then just a single white disc is flipped (in the upper right direction)The white disc in the upper direction is not flipped because there is a gap (empty cell) between the newly placed black disc and the white disc.

If one player cannot make a valid move then the turn is passed to his opponent.  When both players have no legal moves, the game ends.  This occurs in the following situations:

  • the board is full of discs (i.e. there are no empty cells left on the board)
  • one player has no more discs on the board
  • the board is not full and there are discs of both colors on the board but neither player can place a disc that flips at least one opponent's disc.

When the game ends the player with the most discs on the board wins.

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