import pygame
import random
pygame.init()

win = pygame.display.set_mode((500,500))
pygame.display.set_caption("")

circleX = 250
circleY = 0
xSpeed = 10
ySpeed = 10
r = 20
run = True
while run:
    pygame.time.delay(100)

    win.fill((0,0,0))

    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            run = False

    if(circleX < 0 or circleX > 450):
       xSpeed = xSpeed * -1;
       r = r + 5
    if (circleY < 0 or circleY > 450):
       r = r + 5
       ySpeed = ySpeed * -1
    pos = (circleX,circleY)
    circleX = circleX + xSpeed;
    circleY = circleY + ySpeed;
    pygame.draw.circle(win, (255,255,255), pos, r)
          
      
    
    
    
    pygame.display.update() 
    
pygame.quit()