Inversi

The inversi game is played on a conventional 8x8 game board, identical to Reversi (also known as Othello), and with 64 disks, each of which is white on one side and black on the other, again, identical to Reversi.

The rules, however, differ. There are two separate game phases, with different rules.

The first phase is as follows: The game board starts empty, with no disks on it. Each player takes turns placing one disk on the board. No flipping occurs, and both players can choose whether the disk they place is white side up or black side up.

After the last disk is placed (by the second player) the first player chooses who will be white, and who will be black. The game enters the second phase, and the second player moves next.

During the second phase, each player removes a disk of his own color from the board, and flips one or more disks of his own color to his opponent's color.

The board after the move must satisfy the following condition: if the player were to put his tile back on the board, in the location he removed it from, and flip pieces according to the rules of normal Reversi, the result would be identical to the board before he removed his disk.

If a player is unable to make any such move, he must pass. If neither player can legally remove a disk from the board, the game ends.

Whoever has the most disks left on the board at the end of the game wins.

Players may agree to skip the first phase, and start the game with some predetermined pattern (all black, all white, a checkerboard, etc) or have a computer fill the board randomly.