Othello

Overview

Two players place discs on an 8×8 board, flipping the opponent's pieces by bracketing them. Whoever has more discs of their colour when the board fills wins.

Marketed as Othello; the older public-domain version is Reversi, with slightly different opening rules. The slogan — "a minute to learn, a lifetime to master" — is genuinely earned.

This entry is checked against the World Othello Federation's official rules.

1. Setup

An 8×8 board and 64 discs, black on one side and white on the other. Each player takes 32.

Place four discs in the centre in a fixed diagonal pattern: black on e4 and d5, white on d4 and e5.

Black moves first.

2. Placing a disc

A legal move must bracket at least one line of opponent discs between the disc you place and another of your own.

All bracketed discs — horizontally, vertically or diagonally, in every direction at once — are flipped to your colour.

If a move flips nothing, it is illegal. You may not place a disc anywhere you like.

• Only discs in a direct line from the disc you placed flip. Discs that merely look outflanked elsewhere on the board don't.
• You can't skip over your own discs to outflank beyond them.
• Every outflanked disc must be flipped, even when you'd rather not.
• A placed disc never moves to another square.

3. Passing

If you have no legal move, you must pass. You cannot choose to pass when a legal move exists.

If neither player can move, the game ends immediately, even with empty squares remaining.

4. Winning

The game ends when the board is full or neither player can move.

Count the discs. Most of your colour wins. A draw is possible.

5. Strategy

This is where the depth lives, and it is deeply counterintuitive.

Having more discs in the early game is bad. Every disc you own is a disc your opponent might flip. Strong players deliberately minimise their count for most of the game — this is called evaporation.

Corners are permanent. A disc in a corner can never be flipped, because flipping requires bracketing from both sides. Corners are the most valuable squares on the board by a wide margin.

The squares next to corners are poison. The diagonal neighbour — the X square — is the worst square on the board, because occupying it usually hands your opponent the corner.

Mobility beats material. Aim to have many legal moves available and to leave your opponent with few. A player forced to pass repeatedly loses.

6. Reversi differences

Not part of the World Othello Federation rules; included for orientation.

In the original Reversi, players place their first four discs anywhere in the central four squares rather than in a fixed diagonal, and the first four moves are unconstrained.

Commonly argued

• A move that flips nothing is illegal.
• You must pass if you cannot move — and you may not pass otherwise.
• Having fewer discs in the midgame is usually good.
• The game can end before the board is full if neither side can move.
• Corners can never be flipped.
• You must flip every disc you outflank, not just the ones you want.