A simple game on a 3x3 grid, where each side has 3 chess pawns. The objective is to get a pawn to the other side of the board, or leave the opponent unable to move. Normal chess rules apply except that the pawns are not allowed a double move from their starting position. Not really intended as a two-player game, it was designed to demonstrate an artificial intelligence learning technique by using beads in matchboxes. (Old enough to remember matchboxes?) Twenty-four matchboxes were used to represent the possible moves. Essentially, there were two phases. The first phase was to "teach" the matchbox computer to play the game, then a second phase allowed the matchbox computer to play other opponents. The learning speed depended on the skill of the opponent in the teaching phase. There are variants in which taking the opponent's piece is mandatory ("Dawson's chess") and ones that use larger boards. Martin Gardner first published this in his Mathematical Games column in March 1962, and subsequently in his book, "The Unexpected Hanging".