BOARD GAMES have long fascinated artificial-intelligence (AI) researchers. They have clear rules, well-defined playing fields and objective winners and losers. This makes them perfect “sandpits” for training AI software. Sometimes, though, their rules contain glitches. Aficionados of Go will be familiar with ko fights—situations in which the basic rule set would permit a game to carry on for ever, and for which an exception had to be created. Avoiding similar problems in newly invented games is something AI can help with.