under the assumption that the opponent plays the move which is best for him so best so worst for me and the assumption that he I play again the best move and then you have this expecting max three to the end of the game and then you back propagate and then you get the best possible move so that is the optimal strategy which for norman already figured out a long time ago for playing adversarial games luckily or maybe unluckily for the theory it becomes harder the world is not always adversarial so it can be if the other