Othello

1 Overview

Othello (also known as Reversi) is a two-player abstract strategy game played on an 8x8 board. Players take turns placing discs that are black on one side and white on the other. When you place a disc, all opponent discs in a straight line between your new disc and an existing disc of yours are flipped to your color. The player with the most discs showing their color when the board fills wins.

The official tagline is "a minute to learn, a lifetime to master" -- and it is accurate. Othello is extremely accessible but has enormous strategic depth. It is one of the most studied abstract games in artificial intelligence research, second only to Chess and Go in computational analysis.

2 Components

• 8x8 game board (64 squares)
• 64 discs, black on one side and white on the other

3 Setup

1. Place 4 discs in the center 4 squares in a diagonal pattern: Black at d5 and e4, White at d4 and e5 (standard notation).
2. Black always moves first.

The starting position creates a 2x2 diagonal cluster in the very center of the board. All 60 remaining discs start off the board.

4 Gameplay

On your turn, place one of your discs on any empty square that flips at least one opponent disc. If you have no legal moves, you must pass. If neither player can move, the game ends.

You cannot place a disc on a square that does not flip at least one opponent disc. Every legal placement must outflank at least one opponent disc.

5 Flipping Discs

A disc is flipped when it is caught in a straight line (horizontal, vertical, or diagonal) between the newly placed disc and another disc of your color, with no gaps and no empty squares in between.

Example: White discs sit in a row at d4, d5, d6. If you place a Black disc at d3 and already have a Black disc at d7, all White discs between d3 and d7 (at d4, d5, d6) flip to Black.

Multiple directions can be flipped simultaneously from one placement. If your new disc outflanks opponent discs in three different directions at once, all of those opponent discs flip.

6 Winning

The game ends when the board is full or neither player can make a legal move. The player with the most discs showing their color wins. Ties are possible.

Note: having more discs mid-game does not mean you are winning. Othello is famous for dramatic reversals -- a player who appears to be losing with 12 discs can flip 30+ discs in a single move near game end.

7 Strategy Guide

Corners Are Everything

The four corner squares (a1, a8, h1, h8) are the most valuable positions on the board. A corner disc can never be flipped -- it is permanent. Capture corners aggressively. Conversely, never play adjacent to a corner if you don't own it: you risk giving your opponent an easy corner capture.

Fewer Discs Is Often Better Mid-Game

Counter-intuitively, having fewer discs in the middle of the game is often advantageous. Fewer of your discs means fewer pieces your opponent can outflank and flip. The goal is board mobility (number of legal moves), not disc count. This is the hardest concept for beginners to internalize.

Mobility Over Territory

Maximize your own number of legal moves while minimizing your opponent's. A player with 10 legal moves has vastly more options than one with 2. Restricting your opponent's mobility is often more powerful than acquiring territory.

Edge Control

Edge squares (outside the corner-adjacent "danger squares") are stable positions that are hard to flip once established. Build edge chains leading to corners rather than filling the interior of the board.

The X-Squares and C-Squares

Never voluntarily play in the X-squares (b2, b7, g2, g7 -- diagonally adjacent to corners) or C-squares (a2, b1, a7, b8, h2, g1, h7, g8 -- orthogonally adjacent to corners) unless forced. These squares almost always give your opponent access to the adjacent corner.

8 Solved Status and Complexity

Othello on an 8x8 board has approximately 10^28 possible positions -- far more than Chess openings though less total than Chess overall. As of 2024, Othello remains unsolved at the full game level, though perfect endgame play is well-characterized from about 20 empty squares remaining.

Computer programs have dominated human Othello champions since the 1980s. The AI "Logistello" by Michael Buro (1997) and subsequent neural-network-based programs have achieved superhuman play. Despite this, human grandmaster-level play is genuinely impressive and the gap between beginner and expert is enormous.

Othello is popular in AI research as a benchmark for game-playing algorithms because it is simple to implement, computationally tractable, yet strategically complex enough to be interesting.

9 FAQ