How to play Reversi (Othello)

Reversi, better known by its trademarked name Othello, is a strategy classic that takes a minute to learn and a lifetime to master. It is played on an 8×8 board with discs that are black on one side and white on the other. You play one colour against the computer, and the balance of power can swing back and forth right up to the final move. There is nothing to install — pick a colour and start playing.

The goal

Finish the game with more discs of your colour showing than your opponent's. The board starts with four discs in the centre — two black, two white — and play continues until neither side can move, usually when all 64 squares are full.

How to play

• Black always moves first. You can choose to play black or white when you start a new game.
• You may only place a disc where it traps a straight line of your opponent's discs — horizontally, vertically, or diagonally — between the disc you just placed and another disc of your own.
• Every opponent disc you trap in that line flips to your colour. A single move can flip discs in several directions at once.
• If you have no legal move, your turn is passed automatically. The legal squares for your turn are marked on the board to help you see them.

Choose your difficulty

Three difficulty levels set how far the computer looks ahead. Easy thinks just one move deep and is happy to be outmanoeuvred. Medium searches three moves ahead. Hard searches five moves ahead using a positional evaluation that prizes corners and mobility, and gives a genuinely tough game.

Strategy

Corners are gold: once you own a corner it can never be flipped, and it anchors whole edges. The squares diagonally next to a corner — the "X-squares" — are the most dangerous of all early on, because playing there often hands your opponent the corner. Resist the urge to flip the most discs each turn; in the opening and middlegame, having more available moves than your opponent (your "mobility") matters far more than the disc count. A board full of your colour early often means you have run out of good moves later.