Computer poker: The perfect card sharp

Computer says "fold" NOUGHTS and crosses (known as tic-tac-toe in America) is one of the first games children learn. The more inquisitive among them soon realise there are strategies that always win if your opponent makes a mistake, and guarantee a draw even if he does not. (The best is to start out in one of the grid's corners.) When a provably ideal strategy such as this is discovered for any given game, mathematicians describe that game as being "solved".Using computers, quite a few games hav...