Fractal ractangle 2

"""
Draw fractal ractangle programm.

"""

import pygame


BLACK = (0x00, 0x00, 0x00)
WHITE = (0xff, 0xff, 0xff)
GREEN = (0x00, 0xff, 0x00)
RED =   (0xff, 0x00, 0x00)
ALPHA = 0.01


def main():
    """ Main function for the game. """
    global ALPHA


    pygame.init()

    # Set the width and height of the screen [width,height]
    size = [600, 600]
    screen = pygame.display.set_mode(size)

    pygame.display.set_caption("My Game")

    done = False

    clock = pygame.time.Clock()

    def fractal_rectangle(A:tuple, B:tuple, C:tuple, D:tuple,
        depth=10) -> None:
        """ Draw fractal rectangle.
            In: 4 tuple - point coord
                  int - recursion depth """

        if depth < 1:
            return

        for M, N in (A, B), (B, C), (C, D), (D, A):
            pygame.draw.line(screen, BLACK, M, N)


        A1 = (A[0]*(1-ALPHA) + B[0]*ALPHA,
            A[1]*(1-ALPHA) + B[1]*ALPHA)
        B1 = (B[0]*(1-ALPHA) + C[0]*ALPHA,
            B[1]*(1-ALPHA) + C[1]*ALPHA)
        C1 = (C[0]*(1-ALPHA) + D[0]*ALPHA,
            C[1]*(1-ALPHA) + D[1]*ALPHA)
        D1 = (D[0]*(1-ALPHA) + A[0]*ALPHA,
            D[1]*(1-ALPHA) + A[1]*ALPHA)

        fractal_rectangle(A1, B1, C1, D1, depth-1)


    # -------- Main Program Loop -----------
    while not done:
        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                done = True



        screen.fill(WHITE)
        fractal_rectangle((100, 100), (500, 100),
            (500, 500), (100, 500))
        ALPHA += 0.01

        pygame.display.flip()

        clock.tick(60)
    pygame.quit()

if __name__ == "__main__":
    main()