Start of the game
The game is started in the position shown below on a Reversi board consisting of 64 squares in an 8x8 grid. Squares are notated from A1 to H8. Initial position has placed four discs. Each disc has white and black sides and can be flipped to change top color.
To start a game, Black always moves first.
You can play a disc when you flank one or more opponents’ discs between your new disc and any other of your own discs, in the same horizontal, vertical or diagonal line. The opponents discs that are flanked will be turned upside-down and change color. This turning is called flipping.
The below picture demonstrates situation when player performs move the first move f4 then white disc e4 is flipped.
When discs are flanked in multiple directions, these have to be flipped as well. The below example demonstrates situation when white disc may be placed on e2.
Then black disks will be flipped on c4, d3 (diagonally) and e5, e4, e3 (vertically).
When there is no possible legal move, the turn is given back to the opponent. This is called a pass. In the bellow example white is not able to play because he cannot flank any of the black discs with a new disc. White passes and black will move again. After that move, white has to move. If white is still not able to move, he will have to pass again.
If both players need to pass because there is no possible move for any of them, the board game has ended. Usually, this will occur when there are no more empty squares. In some situations, one or more squares remain empty and none of the players have perform move.
Aim of the game
The object of the game is to own more discs than your opponent when the game is over. The game is over when neither player has a move. Then the discs are counted. Whoever has the most discs wins the board game. If the result is 32-32, the board game is a draw. The game also ends when the players agree to finish the game.