Palm Games from Whitehorse -- Software Downloads

The making of ChromaGames for Palm OS

How do you write a chess game when you don't know how to play chess?

We began writing ChromaGames because Electronic Arts ran several months late providing artwork for Tiger Woods Golf. With nothing else to do, Eric saw a chance to experiment with interesting AI strategies. For Bill, it was a way to create a game title that Whitehorse actually owned. Like Tiger, ChromaGames was written mostly in C. It uses a common engine for board drawing, piece movement, etc.

You'll notice one thing missing in those motivations: knowledge of chess. We were utterly ignorant of the game. One of our playtesters, Chris Chu, gently warned us we were in over our heads. But we persevered, and the results were... not bad.

The checkers and chess games use standard tree AI algorithms. They were written from scratch in C, and tested by playing hundreds of random games against GNU chess (Linux). No GPL was used in our software; we simply benchmarked our pre-release builds against GPL software.

ChromaGames checkers and chess employ standard "openings," or initial moves, which are selected at random from an array at runtime. After the opening moves are exhausted, or when the human player makes a move not anticipated by the openings array, the tree AI takes over. We found the standard openings in books at the Stanford University library.

ChromaGames backgammon AI is interesting. It uses the first Palm-based neural network. The network was trained by playing many games against itself; performance improvements were measured by test games versus XGammon. When the neural net performance stabilized, it was frozen and moved over to the Palm. Again, no GPL code was used in our software.

The result, according to our users, is a decent, but unorthodox, computer backgammon player. Since we didn't use any fixed rules of thumb for good backgammon play, the network was trained only by the results of its many games against another computer AI. So our AI DOES understand good defense experientially, but DOESN'T employ standard defenses. It is more aggressive than a "normal" backgammon player, and can be defeated most easily by a very aggressive human player.

For our customers, this has created some consternation. Though nearly everyone loved the game, the two primary complaints are diametrically opposed: first, that the computer is "dumb" because it doesn't employ standard defenses, and second, that the computer "must be cheating" because it wins so often. Bill believes this dichotomy suggests the nonstandard play style actually works pretty well.

Better AI might have been achieved by training against a number of different AI players -- had we the time or resources to do that. Modern Palm handhelds have enough memory and CPU to support live training, which might be another improvement.

We no longer sell ChromaGames, but we do offer a chess game.