What is Octagon Reversi?
Octagon Reversi is played on a 10×10 board with three squares removed at each corner: the corner itself and the two squares next to it along the edges. That leaves an octagon of 88 playable squares. The removed squares are not part of the board: nobody can place a disc there, and no line of discs runs across them.
Everything else follows standard Reversi. The four centre squares start with two discs of each colour placed crosswise, Black moves first, each move must outflank and flip at least one line of opposing discs, and the player with more discs at the end wins.
The cut corners change the strategy. A board with corners has four squares where a disc can never be flipped. The octagon has eight such squares instead: the edge squares on each side of a cut, where an edge now ends, such as c1 and a3. Each of them can be flipped along no line, so it plays like a corner, while the diagonal square inside each cut, such as b2, can still be flipped along one diagonal. With twice as many safe squares, edge fights start earlier and are harder to read.
Rule changes
| Rule | Standard Reversi | Octagon Reversi |
|---|---|---|
| Board | Standard Reversi8×8, 64 squares. | Octagon Reversi10×10 with three squares cut from each corner: an octagon of 88 squares. The board size option is not used. |
| Squares that can never be flipped | Standard ReversiThe four corners. | Octagon ReversiEight squares: the two edge squares beside each cut corner. Lines of discs stop at the cut, so no move can outflank across it. |
| Starting position | Standard ReversiTwo Black and two White discs on the four centre squares, placed crosswise. | Octagon ReversiThe same, on the centre squares of the 10×10 board. |
| End of the game | Standard ReversiWhen neither player can move, at the latest when all 64 squares are filled. | Octagon ReversiWhen neither player can move, at the latest when all 88 squares are filled. |
| Other options | Standard ReversiEvery option in the table setup can be used. | Octagon ReversiWorks with Anti-Reversi, the free opening and blocked squares. There is no corner handicap, because the board has no corners. |
History
Reversi has been played on boards of different shapes for as long as it has existed. John W. Mollett's Game of Annexation, one of the two Victorian games from which Reversi descends, used a cross-shaped board, and computer versions from the early 1990s on have offered boards with many outlines and corner shapes.
In Japan, where the modern game became a national pastime after 1973, makers have sold several special boards next to the standard set, among them a larger 10×10 board. Octagon Reversi follows the same idea of reshaping the board: it takes the 10×10 board and cuts its corners, so the four strongest squares of the standard game turn into eight weaker ones and the edges become the centre of the fight.