Many variants on the concept of noughts and crosses exist. This version was created by Alan Parr. It is played on a 3x3 or 3x4 board with a supply of red, yellow, and green markers. The object is to get a line of three of the same color. On each turn, you may do ONE of the following: (1) Put a red counter in an empty square. (2) Replace a red counter with a yellow one. (3) Replace a yellow counter with a green one. So ultimately the board will fill with green counters. According to the book "What's your Game" by Michael Cornelius & Alan Parr, the game is a first player win with perfect play.