What is Reversi with blocked squares?
In this variant one to four squares are blocked before the first move, chosen at random when the table starts. A blocked square is a hole in the board. Nobody can place a disc on it, and it breaks every line that runs through it: a disc can only outflank opposing discs along a line with no blocked square between them.
The blocked squares are never placed in the central 4×4 area, so the opening is untouched, and never on a corner that holds a handicap disc. The rest of the game follows standard Reversi: Black moves first, each move must outflank and flip at least one line, a player without a legal move passes, and the player with more discs at the end wins.
Holes create new strong points. A disc next to a blocked square cannot be flipped along that line, so the squares around a hole act a little like edges, and a hole near a corner can make the squares beside it much safer than usual. Empty squares can also be left with no legal move from either side, so a game may end before the board is full.
Rule changes
| Rule | Standard Reversi | Reversi with blocked squares |
|---|---|---|
| Board | Standard ReversiEvery square can be played. | Reversi with blocked squaresOne to four squares are blocked, chosen at random when the game starts and kept in the game record, so a replay shows the same board. |
| Where blocks go | Standard ReversiThere are no blocked squares. | Reversi with blocked squaresAnywhere outside the central 4×4 area, on any board size and on the Octagon, but never on a handicap corner. |
| Legal moves | Standard ReversiPlace a disc on any empty square that outflanks at least one line of opposing discs. | Reversi with blocked squaresThe same, but a blocked square can never be played. |
| Flipping | Standard ReversiA line of opposing discs is flipped when it lies between the new disc and another disc of yours. | Reversi with blocked squaresThe same, but a line stops at a blocked square, so nothing is outflanked or flipped across it. |
| End of the game | Standard ReversiWhen neither player can move, usually when all 64 squares are filled. | Reversi with blocked squaresWhen neither player can move. Blocked squares stay empty, and other empty squares can be walled off, so the board may not fill. |
History
Blocked squares have no single inventor and no official rulebook. Reversi players have experimented with the shape of the board since the 19th century, when Mollett's Game of Annexation was played on a cross-shaped board, and boards with holes or obstacles turn up in many computer versions of the game.
The rules used here follow the most common reading of the idea: a blocked square is never played, and it ends every line that runs through it. Placing the blocks at random gives each game a fresh board on which memorised openings and edge patterns help less, while the centre stays free so that every game starts from a normal position.