Reversi on an 8×8 board against the computer at three levels or with a friend on one device. Trap discs to flip them; most discs at the end wins.
What is Reversi?
Reversi is a two-player strategy board game played on an 8×8 board with discs that are dark on one side and light on the other, in which you trap your opponent's discs between your own to flip them to your colour, and the player with more discs on the board at the end wins. Every move changes several discs at once, so the lead can swing back and forth until the very last move.
The rules take a minute to learn. Playing well is another matter: the side with the most discs in the middle of the game is often the one that loses, and the best moves are usually the ones that flip the fewest discs.
How to play Reversi: rules in full
The game starts with four discs in the centre, two of each colour placed diagonally. Dark moves first. On your turn you place one disc of your colour on an empty square so that, in at least one straight line (across, down or diagonal), one or more of your opponent's discs lie between the new disc and another disc of yours with no gaps. All the opponent's discs trapped that way, in every direction at once, flip to your colour.
A move must flip at least one disc. In our game, dots mark every square where you are allowed to play. When you have no legal move, a message announces the pass and your opponent moves again. You cannot pass when a legal move exists.
The game ends when neither side can move, which usually happens when the board is full. The counters above the board show how many discs each side has, and the side with more discs wins. Equal counts are a draw.
Reversi strategy: corners, mobility and parity
Take the corners. A disc in a corner can never be flipped, because there is no square beyond it to trap it from. Corners also anchor the edges next to them, making whole rows of discs permanent. In many games, the player who holds more corners wins.
Avoid the squares next to empty corners. The square diagonally next to a corner, called the X-square, and the two squares beside it along the edges, called C-squares, are dangerous while the corner is empty. A disc there often lets your opponent take the corner. Play them only when the corner is already taken or when you have checked that your opponent cannot use them.
Keep your mobility. Mobility is the number of legal moves you have. A player with many options can wait for good moves, while a player with few may be forced to give away a corner. In the middle of the game, prefer moves that leave your opponent with few replies and you with many.
Flip few discs and stay inside. Discs that touch empty squares, called frontier discs, give your opponent places to play. Quiet moves that flip one or two inner discs, without adding to your frontier, keep the opponent's options low. Grabbing many discs early usually creates a long frontier and hands your opponent good moves later.
Count the endgame. When the board is almost full, it is split into small empty regions. Try to make the last move in each region, since the last move there cannot be answered. On Hard, the computer calculates the final dozen empty squares exactly whenever its time allows, so precise counting is what beats it.
Computer levels and game options
You can play against the computer or with a friend on one device. Against the computer you choose Easy, Medium or Hard, and who moves first. Easy looks only one move ahead and adds randomness on purpose. Medium searches three moves ahead and weighs both square values and mobility. Hard keeps searching deeper for about a second per move and plays the last 12 empty squares perfectly when time allows.
Our game uses the standard 8×8 board with the usual crossed starting position. Other variants exist, such as larger boards or historical rules where players placed the first four discs themselves, but they are not offered here.
The history of Reversi
Reversi was created in England in the 1880s, where two men, Lewis Waterman and John W. Mollett, each claimed to have invented it. It became a popular parlour game in Britain and was later sold in many countries. In the early versions the players placed the first discs on the centre squares themselves.
In the 1970s a version with a fixed starting position, the one used today, was published in Japan under a trademarked name and spread worldwide with clubs and championships. Reversi was also one of the first board games played well by computers, and today programs play it far beyond human level.
Play Reversi free on Hevagames
Reversi runs in the browser on phones, tablets and computers, with no download. Tap or click a marked square to play, or use the arrow keys to move and Enter or Space to place a disc. Flipped discs turn over with a short animation so you can follow every capture.
Undo, with the button or Ctrl+Z, takes back your last move and the computer's reply. If you leave mid-game, the position stays in your browser and the start screen lets you resume it. Wins in a row against the computer are counted as a streak, and in two-player mode a coloured bar and a glow around the board mark the player to move.
How to play
- 1Choose vs Computer (Easy, Medium or Hard, and who moves first) or 2 Players. Dark moves first.
- 2Place a disc so that one or more rival discs lie in a straight line between it and another of your discs. Those discs flip to your colour.
- 3Dots mark every square where you can play. If you have no legal move, your turn is skipped.
- 4The game ends when neither side can move. The counters above the board show who has more discs.
Controls
Tips
- Corners can never be flipped back, so they are worth a lot.
- Avoid the squares next to an empty corner; they often hand the corner to your rival.
- Having more moves available matters more than having more discs in the middle of the game.
