AI Horizon: Intelligence and Reason in Computers
Example Diagram of the Minimax Game Tree

 
NOTE: This minimax game tree shows all possible combinations of the first two moves of Tic-Tac-Toe,
but symmetrical positions have been removed for the sake of simplicity and space.

Assume that red (player 'X') moves first .

Image Created by the People at AI Horizon <http://www.aihorizon.com/>