Reversi Unlimited for Mac

From Xenquin Software:

Reversi is a classic board game. It consists of a playfield, sized 8x8 squares, and black and white tiles. The winner is the player who has more tiles on the board when the game finishes. Initially, there are 2 black and 2 white tiles in the middle of the board, in formation of a square. Each turn, players convert enemy tiles to their own by "surrounding" them. When a tile is placed, all enemy tiles in horizontal, vertical, and diagonal lines which end up into your own color are turned around to your color. If there is not your tile in the end of a line, that line won't be turned. A tile can only be placed in empty square, and must convert at least 1 enemy tile to be a valid move. If there are no valid moves, you have to skip your turn. When the board fills up of tiles, the winner is the one who has more of his/her color on the board.