import pygame, os, sys, random
from pygame.locals import *

pygame.init()
FPS = 30
fpsClock = pygame.time.Clock()
gameSurface = pygame.display.set_mode((640, 480))
pygame.display.set_caption('beginner')

bgImg = pygame.image.load(os.path.join("space_invaders", "space_image.png")).convert()
shipImg = pygame.image.load('ship.bmp').convert()
position = shipImg.get_rect(bottom=480, centerx=random.randrange(640))

while True:
    gameSurface.blit(bgImg, (0,0))
    for event in pygame.event.get():
        if event.type == QUIT:
            pygame.quit()
            sys.exit()
        if event.type == KEYDOWN:
            # keyboard inputs
            if event.key == K_LEFT:
                position.centerx -= 1
            if event.key == K_RIGHT:
                position.centerx += 1
    gameSurface.blit(shipImg, position)
    pygame.display.update()
    fpsClock.tick(FPS)