Rules of the game

Othello is a two-player game played on an 8×8 board with two-sided discs — black on one side, white on the other. One player plays Black, the other White. Once placed, a disc stays on the board until the end of the game; only its colour can change.

The game starts with four discs in the centre of the board, two of each colour, placed crosswise. Black moves first, and then the players take turns.

A move means placing a disc of your colour on an empty square so that an unbroken line of your opponent’s discs lies between it and another disc of your colour — horizontally, vertically or diagonally.

A move that does not close off any such line is not allowed. At the start, Black has four moves to choose from — the dots on the diagram show them.

The opponent’s discs trapped between the new disc and the player’s disc are flipped to the player’s colour. The line must be unbroken — an empty square in between breaks it.

One move can close lines in several directions at once, and then discs are flipped in all of them. All trapped discs must be flipped; you cannot pick only some.

A player with no legal move passes, and the turn goes to the opponent. Passing is not a choice: if a legal move exists, it must be played.

A player may pass several times in a row — the opponent keeps playing until the passing player has a move again.

The game ends when neither player has a legal move. This usually happens when the board is full, but it can come earlier: when only one colour is left on the board, or when nobody can play on any of the remaining empty squares.

The player with more discs of their colour on the board at the end wins. The score is written as both players’ disc counts, for example 33–31.

If the game ends before the board is full, the empty squares go to the winner. In the game from the previous step, Black has 39 discs, White has 3 and 22 squares are empty — so the score is 61–3 to Black.

If both players have the same number of discs, the game is a draw, usually 32–32.