import pygame
import sys

pygame.init()
screen = pygame.display.set_mode( ( 400, 300 ) )
background = pygame.Surface((400, 300))

surface = pygame.Surface(( 10, 10))
surface.fill((0,255,0))

pos = [175, 125]

while True :
    events = pygame.event.get()
    for event in events:
        if event.type == pygame.QUIT :
            pygame.quit()
            sys.exit()
        if event.type == pygame.KEYDOWN :
            if event.key == pygame.K_RIGHT :
                pos[0] += 20
    screen.blit( background, (0,0))
    screen.blit(surface, pos)
    pygame.display.update()