The Gorrion Game Server



The Game of Othello ( Reversi )

Othello ( Reversi ) is a game of strategy played by two people on an 8x8 board. It is known under two names, Othello and Reversi. It is one of the games that can be played online on the Gorrion Server. Please do give it a go. This page gives an introduction to the game.

A game of Othello ( Reversi )

( A game in progress. Black to move. The X squares show where Black may make a custodial entrapment. )

The Game

The game is played with identical disks that are coloured white on one side and black on the other.

One player takes black, the other white. They take turns to place a disk in their colour, and make a custodial entrapment of disks in the opponent's colour. All disks that are caught within an entrapment are turned over to show their opposite colour. The aim is to have the majority of the disks in your colour at the end of the game. Black goes first.

If a player cannot make an entrapment of at least one of the opponent's colours then he misses a go. If neither player may make a move, or when all the squares are occupied, the game is at an end.

Starting Position.  A game starts with the four centre squares occupied in the following configuration.

Othello starting position

( Starting position. )

Entrapments.  A custodial entrapment occurs when you place a disk in your colour so that a line of your opponent's colours is flanked by your colour at both ends. Entrapments can be either in an orthogonal or diagonal direction. In the following diagram if Black plays at 'A' the marked disks will be reversed.

Invalid enclosures Safely connected

( Entrapment. Before and after. )

Multiple entrapments can be made. All disks caught in an entrapment have to be reversed.

Invalid enclosures Safely connected

( Multiple entrapment. Before and after. )

You cannot use the edge of the board to trap. The triangled disks in the following diagram will not be reversed. One consequence of this is that a disk in the corner can never be reversed.

Invalid enclosures Safely connected

( Before and after. A line of edge-connected disks is not reversed. )

Some Insights into Othello / Reversi

Here are a few guidelines for beginners.

You need to play wisely during the opening so that you get a good position in the middle game, and then to play wisely in the middlegame so that you get a good endgame. Early in the game you need usually to reverse few of your opponent's colours, to give him only a small choice of moves, and hope that it will force him eventually to make a bad move. Blindly reversing as many of your opponent's colours as you can will usually lead to defeat.

Disks in the corners can never be reversed. If you get to play there then you usually have an advantage. Likewise do not allow your opponent to play in the corners. How do you do that? Avoid playing in the squares adjacent to the corners and your opponent will not have a way in.

Eventually, though, both of you will be forced to play near the corners and this is when the game becomes interesting.

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The Gorrion Game Server

Othello ( Reversi ) is one of the games played online on my game server, Gorrion. [ ]. Please do join in the fun.

The GoRilla Editor

GoRilla is a game viewer / reader / editor for many game files ( including Othello / Reversi ) stored using the SGF standard [ ]. It is a non-commercial program ( freeware ), and is available from my web page [ gorilla.html ]. I hope you will find it useful.