Jogo em Pygame

import pygame
from pygame.locals import *
from sys import exit
from random import randrange

pygame.init()
pygame.font.init()
pygame.mixer.pre_init(44100, 32, 2, 4096)

font_name = pygame.font.get_default_font()

game_font = pygame.font.SysFont(font_name, 72)

screen = pygame.display.set_mode((800, 600), 0, 32)

background_filename = 'background.jpg'
background = pygame.image.load(background_filename).convert()

ship = {
    'surface': pygame.image.load('rola.png').convert_alpha(),
    'position': [randrange(800), randrange(600)],
    'speed': {
        'x': 0,
        'y': 0
    }
}

explosion_sound = pygame.mixer.Sound('boom.wav')
explosion_played = False
pygame.display.set_caption('BATCABUNDA GAME')

clock = pygame.time.Clock()


def create_asteroid():
    return {
        'surface': pygame.image.load('illuminati.png').convert_alpha(),
        'position': [randrange(792), -64],
        'speed': randrange(1, 11)
    }

ticks_to_asteroid = 90
asteroids = []


def move_asteroids():
    for asteroid in asteroids:
        asteroid['position'][1] += asteroid['speed']


def remove_used_asteroids():
    for asteroid in asteroids:
        if asteroid['position'][1] > 600:
            asteroids.remove(asteroid)


def get_rect(obj):
    return Rect(obj['position'][0],
                obj['position'][1],
                obj['surface'].get_width(),
                obj['surface'].get_height())


def ship_collided():
    ship_rect = get_rect(ship)
    for asteroid in asteroids:
        if ship_rect.colliderect(get_rect(asteroid)):
            return True
    return False

collided = False

while True:

    if not ticks_to_asteroid:
        ticks_to_asteroid = 90
        asteroids.append(create_asteroid())
    else:
        ticks_to_asteroid -= 1

    ship['speed'] = {
        'x': 0,
        'y': 0
    }

    for event in pygame.event.get():
        if event.type == QUIT:
            exit()

    pressed_keys = pygame.key.get_pressed()

    if pressed_keys[K_UP]:
        ship['speed']['y'] = -13
    elif pressed_keys[K_DOWN]:
        ship['speed']['y'] = 13

    if pressed_keys[K_LEFT]:
        ship['speed']['x'] = -13
    elif pressed_keys[K_RIGHT]:
        ship['speed']['x'] = 13

    screen.blit(background, (0, 0))

    move_asteroids()

    for asteroid in asteroids:
        screen.blit(asteroid['surface'], asteroid['position'])

    if not collided:
        collided = ship_collided()
        ship['position'][0] += ship['speed']['x']
        ship['position'][1] += ship['speed']['y']

        screen.blit(ship['surface'], ship['position'])
    else:
        if not explosion_played:
            explosion_played = True
            explosion_sound.play()
            ship['position'][0] += ship['speed']['x']
            ship['position'][1] += ship['speed']['y']

            screen.blit(ship['surface'], ship['position'])
        else:
            text = game_font.render('PIZZA OVER 9000', 1, (255, 0, 0))
            screen.blit(text, (335, 250))

    pygame.display.update()
    time_passed = clock.tick(30)

    remove_used_asteroids()