Reversi on the classic 8×8 board against a computer opponent with three strengths. Legal moves are marked, undo takes back your move and the reply, and a hint suggests a good square. There is no app, no sign-up and no interstitial before play; it works offline after the first visit and every square can be played from the keyboard.
Reversi board is loading.
You: dark Computer: light Legal moveYour turn.
The disc count swings wildly until the very end, so counting discs is a poor guide in the middle game. Strong play is about which squares you hold and how many moves you leave yourself.
A disc in a corner can never be flipped, and it anchors the edges next to it. The squares diagonally next to an empty corner (b2, g2, b7, g7) are the most dangerous on the board: taking one usually hands the corner to your opponent. The edge squares right beside a corner (such as b1 and a2) carry a smaller version of the same risk. Once a corner is yours, its neighbours become safe.
In the opening and middle game, prefer moves that flip few discs and keep your pieces in a compact group. Every disc you flip is a possible target and gives your opponent more choices. The aim is to leave them with only bad moves, so they are forced to give you a corner or an edge.
Edges are stable only when they connect to a corner. A lone disc in the middle of an edge can be sandwiched, and an edge you fill carelessly can give the corner away. Take edge squares when they are safe or when they force a reply.
With a dozen or fewer empty squares, discs start to matter. Look for moves that leave your opponent without a reply so you move twice, and try to make the last move in each empty region.
The computer uses an alpha-beta search and scores positions by square values (corners high, squares next to an empty corner negative), mobility and corners held, and near the end by the disc difference. This page plays at Medium, looking 3 moves ahead (plies). Easy looks 1 move ahead and picks with some randomness among moves close to its best. Hard looks 5 moves ahead. Medium and Hard play the last 8 empty squares perfectly whenever their search budget allows.
Moves are instant on a laptop; Hard averages about 15 milliseconds. The computer is deterministic: the same puzzle code and the same moves always give the same game, so you can replay a game you lost and try something different.
Reversi dates from England in the 1880s, where it was published as a board game and became a popular pastime; two English inventors each claimed it as their own. In early versions the players placed the first four discs themselves. A modern commercial version from the 1970s fixed the crossed starting position and helped bring the game to a worldwide audience; the same start is used here. Reversi is still played in clubs and tournaments around the world.
Each strength keeps its own stats in your browser: games played and games won. A draw counts as played but not won. Reversi is turn-based, so there is no timer and no daily game; the header shows your disc count, the computer’s and your number of moves.
Undo takes back your last move together with the computer’s reply, as far back as you like, and redo works too. The hint runs a three-ply search for you, names the square and how many discs it flips, and can be applied with one click. The first two hints in each game are free; when ads are switched on later, further hints offer a short ad or a 30-second wait. Each game has a puzzle code such as A7K3Q, and ?p= in the address replays the same game.
The 8×8 board fits any phone, the two sides differ in shape as well as colour, and arrow keys with Enter or Space play every move. Tidy Puzzles runs entirely in your browser: there is no app to install, no account to create and no interstitial before you can play. After the first visit the game also works offline, because each puzzle is generated on your device from a seed. Every board can be played with the keyboard alone, on a phone or a desktop, and your stats and unfinished puzzles stay in this browser rather than on a server.
Place a disc so that it traps a straight line of your opponent’s discs between it and another of yours; those discs flip to your colour. If you cannot trap anything you must pass. The player with more discs at the end wins.
Dark. You play dark by default; switch "Play as" to light in settings and the computer opens instead.
The game ends at once, even if squares are still empty, and the discs are counted.
Yes. If both sides have the same number of discs at the end, the game is a draw. It ends the game like a loss would, shows "Draw" and counts as played but not won.
Take corners, avoid the squares diagonally next to an empty corner, and keep your number of possible moves high while limiting your opponent’s. Flipping many discs early is usually a mistake.
Easy looks 1 move ahead, Medium (this page) 3 and Hard 5. Medium and Hard also play the last 8 empty squares perfectly when their search budget allows.
Yes. Undo takes back your move and the computer’s reply together, as many times as you like.
Yes. Arrow keys move between squares, Home and End jump to the row ends, and Enter or Space places a disc.
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Last updated 2026-09-27. Written and maintained by the Tidy Puzzles team; puzzles are generated on your device. How it works.