Extend the standard game-playing environment (Chapter 6) to incorporate a reward signal. Put two reinforcement learning agents into th~e environment (they may, of course, share the agent program) and have them play against each other. Apply the generalized TD update rule (Equation (21.11)) to update the evaluation function. You might wish to start with a simple linear weighted evaluation function and a simlple game, such as tic-tac-toe.