Cube drawing

[deanhystad]

I took a shot at using the minimax algorithm with alpha-beta pruning. This works great in a regular tic-tac-toe game, but not very well in this case.

My first attempt to solve for the tic-tac-toe cube was to treat each face like a separate board and choose the highest score from the three boards. The robot player is fairly responsive in this mode but is easy to beat. The robot has a bias towards the first board, and you can make it waste turns filling empty, but unproductive squares while you set up a win on the 2nd or 3rd board.

My second attempt was to simultaneously solve a tic-tac-toe board with 27 squares. Even if with alpha-beta pruning this is painfully slow. After waiting an hour for the computer to make its first move, I gave up waiting.

In response to your questions.

This is the logic I use to control the robot player:

            elif event.type == pygame.MOUSEBUTTONDOWN:
                if cube.done():
                    # No plays left to make.  Reset for new game
                    cube.reset()
                else:
                    # Check if player clicked on an open square
                    if cube.click(pygame.Vector2(event.pos)):
                        # Player selected a square.  If moves available,
                        # have robot make a play.
                        if not cube.done():
                            cube.draw(surface)
                            cube.play(robot.play(), "O")
                        # Throw away clicks that happened while waiting
                        # for robot player
                        pygame.event.clear()
                    cube.draw(surface)

I changed the Cube.draw() method to make it easier to update the window.

    def draw(self, surface):
        """Draw all the tic-tac-toe boards."""
        surface.fill("white")
        for square in self.squares:
            square.draw(surface)
        pygame.display.flip()