import sys

import pygame

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] += 50
        if event.type == pygame.KEYDOWN:
            if event.key == pygame.K_LEFT:
                pos[0] -= 50
        if event.type == pygame.KEYDOWN:
            if event.key == pygame.K_UP:
                pos[-1] -= 50
        if event.type == pygame.KEYDOWN:
            if event.key == pygame.K_DOWN:
                pos[-1] += 50

    screen.blit(background, (0, 0))
    screen.blit(surface, pos)
    pygame.display.update()