JellyFish is a neural net based backgammon program that plays at a very high level. On the highest playing level it matches the best humans in the world, and on the very fast level 5 a top human will hardly win more than 55% of the time. Also, its use of the doubling cube is outstanding. JellyFish is able to play matches of any length, or ‘money games’ where each point is equally valuable.

JellyFish uses artificial neural networks, trained to play backgammon from self play. An artificial neural network is a model of how the human brain works on the level of individual brain cells. Fredrik Dahl developed the neural nets of JellyFish, and used the neural net compiler nn from Neureka ANS. This program can be used for fun, for testing your game, for analyzing recorded matches, or most importantly:

To improve your game. JellyFish can give a running commentary on the moves and cube decisions you make. You may play against JellyFish, or use the “2 Players” mode to have JellyFish keep track of the score and comment on both opponents play. It’s almost like having your own private professional to comment on your game.

There are four different versions of JellyFish:

  • Light
  • Player
  • Tutor
  • Analyzer

JellyFish Light 3.5 is only available as freeware download
JellyFish Player 3.5 is commercially available, while the previous release (3.0) is available as freeware download
JellyFish Tutor 3.5 is only commercially available
JellyFish Analyzer 3.5 is only commercially available

Why is the software called “JellyFish”?

The name JellyFish comes from the neural net that the program is build over. A neural net is a simulation of a biologic brain, and like a human, JellyFish has learned the strategy of backgammon by experience, by playing itself a very large number of games.

The human brain, however, contains more than neurons, and this is not possible to include into a computer program. The size of our programs “brain” is more the size of some of the lower organism – like a jellyfish. But – our JellyFish is hopefully a better backgammon player than the jellyfish you find in the sea…

System requirements:

JellyFish requires a PC running Windows95 or Windows NT


i486 processor (Pentium recommended for maximum benefit)

2 MB Disk space

CD-ROM Player

Prices & Ordering Information

JellyFish Analyzer 3.5

US $ 220

JellyFish Tutor 3.5

US $ 100

JellyFish Player 3.5

US $ 35

Upgrade Analyzer 2.0 / 3.0 > Analyzer 3.5

US $ 50

Upgrade Tutor 2.0 / 3.0 > Tutor 3.5

US $ 25

Upgrade Player 2.0 / 3.0 > Player 3.5

US $ 20

Upgrade Tutor 2.0 / 3.0 > Analyzer 3.5

US $ 140

Upgrade Player 2.0 / 3.0 > Tutor 3.5

US $ 85

Upgrade Player 2.0 / 3.0 > Analyzer 3.5

US $ 205

Please note that the quoted prices are suggested prices only, and that the actual charge may vary between countries due to reseller practice, local taxes, etc. JellyFish AS accepts no responsibility if the products can not be bought at the prices quoted here. Prices may change without notice.



Gammon Press
P O Box 294
Arlington, MA 02476
Phone: + 1 781 641 2091
Fax: + 1 781 641 2660
Rest of the world:

A & K Klassische Spiele
Grüner Weg 14
34117 Kassel
Phone: + 49 561 89 87 68
Fax: + 49 561 989 20 71

You can now download a free copy of JellyFish 3.5 Light for your evaluation.

To download and install, please follow these steps:

Click the link JellyFish Light 3.5 32-bit ( 1.5 MB, for use with Windows 95 / NT ) and save the file to a temporary directory on your computer.

Run the file JFL3532z.exe and unzip the files

Run the file Install.exe to install JellyFish. Instructions will be given on the screen during the installation process.
Note: JellyFish Light is, as the name indicates, a stripped version with some features disabled. You will see that several of the menu choices are unavailable, as well as some buttons in the dialog boxes. These features are only available in the comersial versions (Player/Tutor/Analyzer) of JellyFish. However, all playing levels are intact, and your JellyFish plays on the same strength as any other JellyFish!