How to play Reversi
Reversi is played on an 8 by 8 board by two players, one with black discs and one with white. You play Black and always move first; the computer plays White. The game begins with two discs of each colour in the centre.
On your turn you place one disc on an empty square so that it outflanks at least one line of the computer's discs. A line can run horizontally, vertically or diagonally, and it is outflanked when your new disc and another of your discs sit at either end of an unbroken row of white discs. Every outflanked disc flips to black. One move can flip lines in several directions at once.
- Squares where you can legally move are marked with a small dot. Only those squares accept a click.
- The most recent move is marked with a small red dot so you can see what the computer just played.
- If a player has no legal move, that turn is passed and the other player moves again. A message tells you when this happens.
- The game ends when neither player can move, usually when the board is full.
The player with more discs at the end wins. The counters at the top show the current disc totals, and your number of wins is saved in this browser. Choose Easy for a relaxed opponent that plays random legal moves, or Hard for one that looks several moves ahead.
Controls
| Desktop | Click any square marked with a small dot to place a black disc there. |
|---|---|
| Mobile | Tap a square marked with a dot to play your move. The computer replies automatically. |
Tips and strategy
Corners are king
A disc in a corner can never be flipped, because there is no way to outflank it. Corners also anchor the edges next to them, letting you build rows of permanent discs. Taking a corner is almost always a strong move.
Avoid the squares next to empty corners
The three squares touching each corner are dangerous while that corner is empty. The diagonal one is especially risky: if you place a disc there, you often hand the corner to your opponent. Only play there when the corner is already taken or when you have no reasonable alternative.
Fewer discs early can mean more later
It feels natural to flip as many discs as possible, but in the opening and middle game this usually backfires. Owning lots of discs gives your opponent more targets and more moves. Strong players aim for:
- Mobility: keep your own options open while limiting your opponent's. A position where the computer has only bad moves is a winning one.
- Quiet moves: prefer moves that flip few discs, especially inner discs that do not open new squares for the opponent.
- Compact groups: keep your discs in the middle of the board rather than spread along the frontier next to empty squares.
Be careful on the edges
Edge squares are safer than most, since they can only be flipped along the edge itself. However, an edge disc can still be captured if the opponent can land on both sides of it. Think twice before giving the computer a chance to slide into a corner along an edge you started.
Count at the end
In the final dozen moves, disc count becomes everything. Look for moves that flip long lines and for chances to force the computer to pass, which can give you two moves in a row. On Hard the computer calculates the ending carefully, so plan ahead too.
About Reversi
Reversi is a two-player strategy game whose rules were published in England in the late nineteenth century. Its central idea, capturing by surrounding lines of an opponent's pieces and turning them over, has kept it popular for well over a hundred years, and it is still played in clubs and tournaments around the world today.
The game is a favourite among computer scientists as well. Its simple rules and fixed board make it a classic test bed for game-playing programs, and modern programs play far beyond human level.
This version is our own implementation for the browser. You play Black against a computer opponent with two settings: Easy picks random legal moves, while Hard searches several moves ahead and values corners, edges and mobility. Everything runs on your device, with no account needed.
Frequently asked questions
Who moves first?
You play Black and always make the first move. The computer plays White.
What happens if I have no legal moves?
Your turn is passed automatically and the computer moves again. If neither side can move, the game ends and the discs are counted.
How strong is the Hard computer?
Hard looks several moves ahead and weighs corners, edges and the number of moves available to each side. Near the end of the game it searches deeper. It is a solid challenge for casual players, though not a match for expert-level programs.
Can I change difficulty in the middle of a game?
Yes. The new setting applies from the computer's next move. Press New to start a fresh game at the chosen level.
