Reversi

Outflank the computer on an 8 × 8 board: every disc you trap in a line flips to your side. Most discs at the end wins.

EasyMediumHard

You: 2
AI: 2

Won: 0
Lost: 0
Drawn: 0

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Click a marked square to play there. Arrow keys move between squares; Enter plays.Tap a marked square to play there.

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About Reversi

Reversi is a classic two-player strategy game, played on an 8 × 8 board with discs that are dark on one side and light on the other. Every move must trap at least one line of the opponent’s discs between the new disc and one of your own, and every trapped disc flips to your colour. When neither player can move, whoever has more discs wins.

Here you play the dark discs against a computer opponent. The rules take a minute to learn, but the game can swing completely in the last few moves, which is what makes it so replayable.

How to play Reversi

Choose how strong the AI should be: Easy (looks one move ahead and often slips up), Medium (looks three moves ahead and values the corners) or Hard (looks five moves ahead and plays the ending perfectly).
The board starts with two dark and two light discs crossed in the centre. Squares where you can play are marked with a small ring.
Click or tap a marked square. Every line of light discs between your new disc and another dark disc flips to dark, in any direction: across, up and down, or diagonally.
The AI then plays a light disc the same way. Whoever opened this game, the other side opens the next.
If one side has no legal move, it passes and the other side plays again. When neither side can move, the game ends and the discs are counted.

Reversi controls

Keyboard
Play on a square	Click it, or Enter or Space on the focused square
Move between squares	Arrow keys (Tab reaches the board)
New game	N
Sound on or off	M

Touch screens
Play on a square	Tap a marked square

Reversi rules

Legal moves

A move must outflank: placing your disc has to trap one or more of the opponent’s discs in a straight line between it and another of your discs, with no gaps. A single move can trap several lines at once, and all of them flip.

You cannot play anywhere else. If you have no legal move you must pass, and the game moves on to the other side; you never pass while a legal move exists.

Winning

The game ends when neither side can move, usually when the board is full. The side with more discs wins; equal numbers are a draw. Your wins, losses and draws at each level are kept in this browser.

The AI levels

Easy looks one move ahead and often plays a random legal move. Medium looks three moves ahead and knows the value of corners and edges. Hard looks five moves ahead and, once 8 or fewer squares are left, searches every possible ending.

Tips and strategy

Corners can never be flipped. Take them when you can, and avoid giving them away.
Be careful with the squares diagonally next to an empty corner: playing there often hands the corner to your opponent.
Flipping lots of discs early is rarely good. Fewer discs and more choices of move usually beat a big early lead.
Edges are strong once they connect to a corner, but an edge disc on its own can be outflanked along the edge.
Try to leave your opponent with few legal moves, so they are forced into bad ones.