How to Play Reversi

Reversi (also known as Othello) is played on an 8x8 board. The game begins with four discs placed in the center: two Black and two White, arranged diagonally.

Black always moves first. Players take turns placing one disc per turn on an empty square.

To make a valid move, you must place a disc so that it outflanks at least one opponent disc. Outflanking means your new disc and an existing disc of your color form a straight line (horizontal, vertical, or diagonal) with one or more opponent discs in between.

All outflanked discs are flipped to your color. Here, Black has placed at D3 (row 2, col 3), outflanking the White disc at D4 and flipping it to Black.

A single placement can outflank opponent discs in multiple directions at once — horizontally, vertically, and diagonally. All outflanked discs in every direction are flipped simultaneously.

In this position, if Black places at E2 (row 1, col 4), it outflanks White discs going down (E3), diagonally down-left (D3), and diagonally down-right (F3) — flipping all of them in one move. Look for moves that flip in multiple directions to maximize your advantage.

If a player has no valid placement that outflanks at least one opponent disc, they must pass their turn. The other player then continues.

If both players have no valid moves in a row, the game ends immediately.

In this board position, White has no moves that outflank any Black disc. White must pass, and Black plays again.

Corners are the most valuable squares on the board. Once a disc is placed in a corner, it can never be outflanked because there are no squares beyond it in any direction.

Corner discs serve as permanent anchors that let you build stable chains along edges. Always try to capture corners, and avoid giving your opponent moves adjacent to corners (the "X-squares" diagonally next to corners and "C-squares" directly next to corners) which often lead to losing the corner.

A disc is stable when it can never be flipped for the rest of the game. Corner discs are always stable. Discs along an edge become stable when they form an unbroken chain connected to a corner of the same color.

Stable discs are guaranteed points at the end of the game. Building from corners outward along the edges is a core strategy. In this position, Black's entire top edge is stable — none of those discs can ever be flipped.

In Anti-Reversi (misere mode), the player with fewer discs wins! This completely flips the strategy: instead of capturing as many discs as possible, you want to minimize your own disc count.

Try to force your opponent to flip your pieces to their color. Moves that would be terrible in normal Reversi — like giving up corners — can become brilliant in Anti-Reversi because your opponent gains discs they don't want.

The same board, same rules for placement and flipping, but a completely different game.