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
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