Смайлик, отскакивающий от стенок окна

import pygame
import sys
import math
 
size = width, height = 800, 600
black = 0, 0, 0
 
 
def main():
    pygame.init()
 
    screen = pygame.display.set_mode(size)
    game_over = False
    smile_x = 150
    smile_y = 150
    circle1_x = 100
    circle1_y = 100
    circle2_x = 200
    circle2_y = 100
    mouth_x1 = 85
    mouth_x2 = 145
    mouth_y1 = 150
    mouth_y2 = 150
    while not game_over:
        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                game_over = True
        if smile_x < 800 or smile_y < 800:
            screen.fill(black)
            smile_x += 1
            smile_y += 1
            circle1_x += 1
            circle1_y += 1
            circle2_x += 1
            circle2_y += 1
            mouth_x1 += 1
            mouth_x2 += 1
            mouth_y1 += 1
            mouth_y2 += 1
        else:
            pass
        pygame.draw.circle(screen, (0, 255, 0), (smile_x, smile_y), 150)
        pygame.draw.circle(screen, (255, 255, 255), (circle1_x, circle1_y), 30)
        pygame.draw.circle(screen, (255, 255, 255), (circle2_x, circle2_y), 30)
        pygame.draw.arc(screen, (255, 0, 0), (mouth_x1, mouth_y1, 70, 70), math.pi, 2 * math.pi, 5)
        pygame.draw.arc(screen, (255, 0, 0), (mouth_x2, mouth_y2, 70, 70), math.pi, 2 * math.pi, 5)
        pygame.display.flip()
        pygame.time.wait(10)
 
 
if __name__ == '__main__':
    main()
    pygame.quit()

import pygame
import sys
import math
 
size = width, height = 800, 600
black = 0, 0, 0
 
 
def main():
    pygame.init()
 
    screen = pygame.display.set_mode(size)
    game_over = False
    smile_x = 150
    smile_y = 150
    circle1_x = 100
    circle1_y = 100
    circle2_x = 200
    circle2_y = 100
    mouth_x1 = 85
    mouth_x2 = 145
    mouth_y1 = 150
    mouth_y2 = 150
    dx = 1
    dy = 1
    while not game_over:
        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                game_over = True
        screen.fill(black)
        smile_x += dx
        smile_y += dy
        circle1_x += dx
        circle1_y += dy
        circle2_x += dx
        circle2_y += dy
        mouth_x1 += dx
        mouth_x2 += dx
        mouth_y1 += dy
        mouth_y2 += dy
        if smile_y > 450 or smile_y < 150:
            dy *= -1
        if smile_x > 650 or smile_x < 150:
            dx *= -1
 
         
        pygame.draw.circle(screen, (0, 255, 0), (smile_x, smile_y), 150)
        pygame.draw.circle(screen, (255, 255, 255), (circle1_x, circle1_y), 30)
        pygame.draw.circle(screen, (255, 255, 255), (circle2_x, circle2_y), 30)
        pygame.draw.arc(screen, (255, 0, 0), (mouth_x1, mouth_y1, 70, 70), math.pi, 2 * math.pi, 5)
        pygame.draw.arc(screen, (255, 0, 0), (mouth_x2, mouth_y2, 70, 70), math.pi, 2 * math.pi, 5)
        pygame.display.flip()
        pygame.time.wait(10)
 
 
if __name__ == '__main__':
    main()
    pygame.quit()