我用PyGame模块在Python中创建了一个太空入侵者克隆，但是当它们到达游戏屏幕的边缘时，我遇到了一些困难。在

当外星人到达游戏屏幕的边缘时，他们会同时改变方向并下降一个关卡？在import pygame

import random

class spaceInvader(pygame.sprite.Sprite):

def __init__(self):

self.image = pygame.image.load("spaceInvader.png")

self.x = 200

self.y = 390

self.shots = []

def handle_keys(self):

key = pygame.key.get_pressed()

dist = 5

if key[pygame.K_RIGHT]:

self.x+=dist

elif key[pygame.K_LEFT]:

self.x-=dist

def draw(self, surface):

surface.blit(self.image,(self.x,self.y))

for s in self.shots:

s.draw(screen)

class Alien(pygame.sprite.Sprite):

def __init__(self,x,y,direction,alienType):

pygame.sprite.Sprite.__init__(self)

self.AlienType = alienType

self.Direction = direction

if alienType == 1:

alienImage = pygame.image.load("alien1.png")

self.Speed = 1

self.Score = 5

if alienType == 2:

alienImage = pygame.image.load("alien2.png")

self.Score = 15

self.Speed = 1

if alienType == 3:

alienImage = pygame.image.load("alien3.png")

self.Score = 10

self.Speed = 1

if alienType == 4:

alienImage = pygame.image.load("alien4.png")

self.Score = 20

self.Speed = 1

if alienType == 5:

alienImage = pygame.image.load("alien5.png")

self.Score = 25

self.Speed = 1

self.image = pygame.Surface([26, 50])

self.image.set_colorkey(black)

self.image.blit(alienImage,(0,0))

self.rect = self.image.get_rect()

self.rect.x = x

self.rect.y = y

def moveAliens(self):

if self.Direction == "right":

self.rect.x += self.Speed

if self.Direction == "left":

self.rect.x -= self.Speed

pygame.init()

pygame.mouse.set_visible(False)

screen = pygame.display.set_mode([400,400])

allAliens = pygame.sprite.Group()

spaceInvader = spaceInvader()

pygame.display.set_caption("Space Attack")

background_image = pygame.image.load("Galaxy.png").convert()

pygame.mouse.set_visible(True)

done = False

clock = pygame.time.Clock()

black =( 0, 0, 0)

white =( 255,255,255)

red = (255, 0, 0)

score = 0

enemies = []

#For X coords

spawnPositions = [50,100,150,200,250,300,350]

yCoord = 10

for n in range(5):

for i in range(len(spawnPositions)):

xCoord = spawnPositions[i]

alienType = random.randint(1,5)

alien = Alien(xCoord, yCoord,"right", alienType)

allAliens.add(alien)

yCoord = yCoord + 15

loop = 0

while done == False:

for event in pygame.event.get():

if event.type == pygame.QUIT:

done = True

for alien in (allAliens.sprites()):

if alien.rect.x < 0:

alien.rect.y = alien.rect.y + 15

alien.Direction = "right"

if alien.rect.x > 395:

alien.rect.y = alien.rect.y + 15

alien.Direction = "left"

loop =+1

for alien in (allAliens.sprites()):

alien.moveAliens()

spaceInvader.handle_keys()

screen.blit(background_image,[0,0])

spaceInvader.draw(screen)

allAliens.draw(screen)

pygame.display.flip()

clock.tick(20)

pygame.quit()

谢谢。在