Reversi

How to play Reversi

Reversi is a classic strategy board game for two players, played on an 8×8 board with discs that are black on one side and white on the other. The rules take a minute to learn — place a disc, trap enemy discs between your own, and watch them flip to your colour — but the game is famous for dramatic last-minute reversals: a board that looks hopelessly lost can swing completely in the final few moves. Play a friend on the same screen, or challenge the computer at three difficulty levels and earn ranking points for every win.

The goal

Have the most discs of your colour on the board when the game ends. The totals swing constantly as discs flip back and forth, so do not panic if you are behind early — in Reversi the score only truly matters on the very last move. Games are usually decided by corner control and mobility, not by who holds more discs in the middle of the game.

The board and setup

The game begins with four discs on the centre squares of the 8×8 board: two black and two white, arranged diagonally. Black always moves first, then the players alternate. In this app the side to move is ringed next to the live disc count, and every square where you may legally play is marked with a small dot — you never have to guess where you can go.

How moves work

• On your turn you place one disc of your colour on an empty square. The placement is only legal if it outflanks at least one enemy disc — the new disc and another disc of yours must trap one or more enemy discs in a straight, unbroken line between them.
• Every enemy disc trapped that way immediately flips to your colour. Flipping is not optional and not selective: ALL outflanked discs flip, in every direction where your move closed a line.
• Lines count in all eight directions — horizontal, vertical and diagonal. One well-placed disc can close several lines at once and flip a large group of discs in a single spectacular move.
• If you have no legal move on your turn, you must pass and your opponent plays again. This app passes automatically and shows a notice, so you always know why the turn came back. You may never pass voluntarily while a legal move exists.
• The game ends when the board is full, or when neither player has a legal move (a double pass). The discs are then counted and the higher total wins.

Winning

When the game ends, each side’s discs are counted and the player with more discs wins; an equal count is a draw, which is a perfectly normal Reversi result. Because a single late move can flip a dozen discs at once, many games are decided on the very last placement — never resign early.

Playing the computer (ranked)

In “Reversi vs Computer” you pick a colour and a difficulty — Easy, Normal or Expert. The computer weighs corner control, mobility and disc totals, and it thinks entirely on your device, so the game works offline. Beat it to earn ranking points: Easy +10, Normal +30, Expert +100. Sign in and your best result appears on the leaderboard. Expert plays a serious positional game — grab your corners before it does.

Strategy tips

• Corners win games. A disc in a corner can never be flipped, and it anchors whole edges of stable discs. Almost any sacrifice is worth a corner.
• Avoid the X and C squares — the squares diagonally and orthogonally next to an empty corner. Playing there usually hands your opponent that corner. They only become safe once the corner is settled.
• Fewer discs early is often better. Aim to keep your disc count low and your options wide in the opening and middle game; a huge wall of your colour just gives the opponent targets and moves.
• Fight for mobility. If you can force your opponent into a position with only bad moves — or none at all, so they must pass — you dictate the endgame.
• Count before the last few moves. Endgames are pure arithmetic: work out which of the final squares flips more discs your way, and remember who gets the last move.

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