Вроде моя новая идея.

import pygame
import random

pygame.init()
w  = 500
h = 500
screen = pygame.display.set_mode([w,h])

running = True

x = 250
y = 250
r = 50
direction = 1
screen.fill((255,255,255))
while running:
    for event in pygame.event.get():

        if event.type == pygame.QUIT:
            running = False
        if event.type == pygame.MOUSEMOTION:
           
           x = event.pos[0]
           y = event.pos[1]
           if (direction == 1):
            r = r - 1
           if (direction == 2):
            r = r + 1
           if (r > 50):
            direction = 1
           if (r < 1):
            direction = 2

    pygame.draw.circle(screen, (255,255, 0),(x, y), r)

    pygame.display.update()

pygame.quit()