Reversi

Reversi is an 8 × 8 board game in which you trap your opponent's discs between two of yours to flip them to your colour. Play against the computer or with two players taking turns on one screen.

How to use

1. Under "Opponent", choose "Computer" or "Two players, one screen". Against the computer, choose "You play" (Black or White) and the "Computer level".
2. Tap a marked square to place a disc; all trapped discs flip. You can also move with the arrow keys and place with Enter.
3. Press "Undo" to take back a move. Every move is listed under "Moves".
4. When neither side can move, the game ends and the disc count decides the winner. Press "New game" to play again.

How it works

• The game starts with two black and two white discs in the centre, and Black moves first. You may only play where you trap at least one opposing disc across, down or diagonally.
• A player with no legal move passes automatically. Switch off "Show the squares where you can play" to play without the markers.
• The computer looks a few moves ahead. Near the end (12 or fewer empty squares on "Hard", 8 on "Medium") it tries to calculate to the last move.
• The game in progress and your record against the computer are saved in this browser.

Questions and answers

What are the rules of Reversi?

Place a disc so that a line of your opponent's discs lies between it and another of your discs, across, down or diagonally; those discs flip to your colour. The game ends when the 64 squares are full or neither side can move, and more discs wins.

Why are corners important in Reversi?

A disc in a corner can never be trapped, so it can never be flipped. Holding a corner also makes the discs next to it easier to keep.

Can a game end in a draw?

Yes. If both colours have the same number of discs at the end, it is a draw; on a full board that is 32 to 32.