1.The Tic-Tac-Toe program considers only the next possible move in the game. Programs that play serious games of strategy, like chess, look far deeper into the consequences of individual moves, considering many levels of moves and countermoves. And today’s computers can examine a huge number of game positions. Specialized machines, like IBM’s chess-playing Deep Blue computer, which beat world champion Garry Kasparov, can examine far more. Deep Blue is able to explore over 200,000,000 board positions per second. That sounds quite impressive, until you realize that the total number of board positions in a complete search for chess is estimated to be over 100,000,000,000,000,000, 000,000,000,000,000,000,000,000,000,000,000, which means it would take Deep Blue more than 1,585,489,599,188,229 years to look at all those possible positions. (The universe, by the way, is estimated to be only 15,000,000,000 years old.)