import pygame, sys

pygame.init()

windowSize = (800,600)

screen = pygame.display.set_mode(windowSize)

myriadProFont = pygame.font.SysFont("Myriad Pro", 48)

helloWorld = myriadProFont.render("Hello World", 1, (255,0,255), (255,255,255))

helloWorldSize = helloWorld.get_size()

x,y = 0,0

directionX, directionY = 1, 1

clock = pygame.time.Clock()

while 1:

    clock.tick(40)
    
    for event in pygame.event.get():
        if event.type == pygame.QUIT: sys.exit()

    screen.fill((0,0,0))
        
    screen.blit(helloWorld, (x,y))

    x += 5 * directionX
    y += 5 * directionY

    if x+helloWorldSize[0] > 800 or x <= 0:
        directionX *= -1
    if y+helloWorldSize[1] > 600 or y <= 0:
        directionY *= -1
    
    pygame.display.update()