class Ship():
    def __init__(self, screen):
     	"""Initialize the ship and set its starting position."""
    	self.screen = screen
    	self.image = pygame.image.load('images/ship.bmp')
    	self.rect = self.image.get_rect()
   		self.screen_rect = screen.get_rect()
    	self.rect.centerx = self.screen_rect.centerx
    	self.rect.bottom = self.screen_rect.bottom
	def blitme(self):
    	"""Draw the ship at its current location."""
    	self.screen.blit(self.image, self.rect)