(define over?
       (lambda (game-state)
         (= (total-size game-state) 0)))
     
     (define total-size
       (lambda (game-state)
         (+ (size-of-pile game-state 1)
            (size-of-pile game-state 2))))
     
     (define announce-winner
       (lambda (player)
         (if (equal? player 'human)
             (display "You lose. Better luck next time.")
             (display "You win. Congratulations."))))