pygame_firstMovement.py

import pygame
import sys #will use the exit function

#Loads all the main pygame modules and initializes them
pygame.init()

screen_width=640
screen_height=480

blue = (0,0,255)

location = [320,240]
direction = [1,1]
radius = 30

DELAYTIME = 10

#Create a new Surface with the dimensions listed above
screen=pygame.display.set_mode((screen_width, screen_height))

#Loop forever:
while True:
    
    #The following makes the window close when clicking the "X" or exit button
    #Without this, the window will not close, and will need to be killed
    #with the task manager
    for event in pygame.event.get():
        if event.type == pygame.QUIT: sys.exit()
    
    screen.fill((0,0,0))
        
    #(surface, color, center, radius)
    pygame.draw.circle(screen, blue, location, 30)
    
    #move the circle
    location[0] += direction[0]
    location[1] += direction[1]
    
    if location[0] <= radius: direction[0] = 1
    if location[0] >= screen_width-radius: direction[0] = -1
    if location[1] <= radius: direction[1] = 1
    if location[1] >= screen_height-radius: direction[1] = -1
    
    pygame.time.delay(DELAYTIME)
        
    pygame.display.flip()