Rules of Othello

• A Board, divided into 8x8 squares. Color is not important, but the commercial boards are typically green with black lines dividing the board into the 64 squares. Some boards contain a border with labels to identify the squares individually. This feature is not required, but is helpful in game analysis, so the boards shown here will have it.

• 64 Discs, each disc white on one side and black on the other. These discs are placed in the squares on the board, like checkers, not on the intersections as is done in the go family of games.

• Clock (required for tournament play), times the moves for each player. Optional for non-tournament play (if you will be competing, it is a good idea to play with the clock beforehand so that you are comfortable with it in competition). Clocks have two displays, one for each player, and a button controlling each. When a button is pressed, the display below it stops counting down and the other display starts counting down.

Two players: one player places discs white side up, the other player places discs black side up.

Four discs are placed in the board's center as shown. The yellow discs on the board to the right show all the locations possible for the first play.

• One player placed discs white side up, the other player places discs black side up. The first play is always made by black.
• Players take turns making legal moves with their color pieces.
• If any mistake made flipping the discs is discovered prior to the other player taking his turn, it must be corrected. If a clock is being used, the mistake is corrected on the errant player's time.
• If any mistake made flipping the discs is discovered after another move has been made, the mistake stands.
• A common rule in competitive play is that once a disc has been placed in a square, if the move is legal it must be made. This is optional in non-tournament play, and the observance or non-observance of this rule should be agreed upon in advance.

• Any move that does not meet all these criteria is not a legal move.
• To simplify the instructions, the following terms are used:
  • Discs of the same color are friendly discs.
  • Discs of opposing colors are hostile discs.
  • Empty squares on the board are neutral.
  • Squares containing a friendly disc are friendly
  • squares containing hostile discs are hostile.
  • Squares touching one another on any side or corner are neighbors.

• Moves must occur on a neutral square with at least one hostile neighbor.
• For each hostile neighbor of the square being considered, continue in a straight line from that neutral square through the neighbor, until either:
  • another neutral square is reached
  • a friendly square is reached
  • the edge of the board is reached.
  If none of the directions reach a friendly square the move is not legal.
• If there are zero legal moves available, the player must pass, and the opponent takes another turn. If neither player can play, the game is over.
• If there is one move available that would flip at least one disc over, that move must be made. This is called a forced move.
• If there are two or more moves available that would flip at least one disc over, one of the available moves must be taken. Which of the plays will be made is left to the discretion of the player.

• If neither player has a move available, the game is over.
• If both players have the same number of discs showing, the game is a draw.
• (Japan) Empty squares are counted, and divided between the players (fractional scores may occur).
• (Europe and World Othello Championship) Any unfilled spaces on the board are awarded to the player with the most discs showing (see the counting diagram).
• (USA) If a player has no discs on the board, the game is scored as 64 to 0. If there are discs of both colors, empty squares are ignored.
• (clock, not usa) If either player runs out of time, the player with time remaining wins 64 to 0.
• (clock, usa) USOA time rules are considerably more complex:
  1. If one player runs out of time, the other player wins. Play continues only to determine the exact score.
  2. When either player runs out of time, they are given a two minute extension.
  3. If either player exceeds the two minute extension the game is stopped.
     • If the loser exceeds the extension, the game is scored as 64 to 0.
     • If the winner exceeds the extension, the game is scored as 32 to 31.
  4. If the game is completed count as one would count a normal game.
  5. If the final count gives the losing player a winning score, the game is scored as 32 to 31 for the winner.
• (clock, world othello championship) Clock rules for the WOC is the same as clock rules for the USOA, except that the defaulting score is 33 to 31 instead of 32 to 31.