Each reversi piece has a black side and a white side. On your turn, you place one piece on the board with your color facing up. You must place the piece so that an opponent's piece, or a row of opponent's pieces, is flanked by your pieces. All of the opponent's pieces between your pieces are then turned over to become your color.
The object of the game is to own more pieces than your opponent when the game is over. The game is over when neither player has a move. Usually, this means the board is full.
The game is started in the position shown below on a reversi board consisting of 64 squares in an 8x8 grid.
A move consists of placing one piece on an empty square. The empty circles show you where a valid move is.
You can capture vertical, horizontal, and diagonal rows of pieces. Also, you can capture more than one row at once.
The game ends when one player wins, by making his color dominant on the board while no moves are left.
In this example White wins.