敌人精灵
首先定义Mob（小怪物）类型：
class Mob(pygame.sprite.Sprite): def __init__(self): pygame.sprite.Sprite.__init__(self) self.image = pygame.Surface((30, 40)) self.image.fill(RED) self.rect = self.image.get_rect() self.rect.x = random.randrange(WIDTH - self.rect.width) self.rect.y = random.randrange(-100, -40) self.speedy = random.randrange(1, 8)
这里的关键是为小怪物初始化一个好的位置。选择一个高于顶部的值（y <0）和一个介于左右两边之间的x的随机值。
在update函数中，更新精灵y轴的坐标，向下移动精灵；精灵离开底部时，通过将精灵移回顶部上方的随机位置来制造下一个精灵。
def update(self): self.rect.y += self.speedy if self.rect.top > HEIGHT + 10: self.rect.x = random.randrange(WIDTH - self.rect.width) self.rect.y = random.randrange(-100, -40) self.speedy = random.randrange(1, 8)
一群敌机
使用for语句，循环创建一些怪物，并将它们添加到精灵组中：
player = Player() all_sprites.add(player) for i in range(8): m = Mob() all_sprites.add(m) mobs.add(m)
现在应该有一群怪物涌入屏幕，如下所示：
这很棒，但让小怪直接向下移动有点无聊。让在x方向上添加一点运动：
class Mob(pygame.sprite.Sprite): def __init__(self): pygame.sprite.Sprite.__init__(self) self.image = pygame.Surface((30, 40)) self.image.fill(RED) self.rect = self.image.get_rect() self.rect.x = random.randrange(WIDTH - self.rect.width) self.rect.y = random.randrange(-100, -40) self.speedy = random.randrange(1, 8) self.speedx = random.randrange(-3, 3) def update(self): self.rect.x += self.speedx self.rect.y += self.speedy if self.rect.top > HEIGHT + 10 or self.rect.left < -25 or self.rect.right > WIDTH + 20: self.rect.x = random.randrange(WIDTH - self.rect.width) self.rect.y = random.randrange(-100, -40) self.speedy = random.randrange(1, 8)
请注意，更改了怪物移出屏幕的判断语句。对角线移动的怪物可能会在它离开底部之前就离开侧面。
if self.rect.top > HEIGHT + 10 or self.rect.left < -25 or self.rect.right > WIDTH + 20:
你的游戏现在应该是这样的：
整合到一起
# Shmup game - part 2 # Video link: https://www.youtube.com/watch?v=-5GNbL33hz0 # Enemy sprites import pygame import random WIDTH = 480 HEIGHT = 600 FPS = 60 # define colors WHITE = (255, 255, 255) BLACK = (0, 0, 0) RED = (255, 0, 0) GREEN = (0, 255, 0) BLUE = (0, 0, 255) YELLOW = (255, 255, 0) # initialize pygame and create window pygame.init() pygame.mixer.init() screen = pygame.display.set_mode((WIDTH, HEIGHT)) pygame.display.set_caption("Shmup!") clock = pygame.time.Clock() class Player(pygame.sprite.Sprite): def __init__(self): pygame.sprite.Sprite.__init__(self) self.image = pygame.Surface((50, 40)) self.image.fill(GREEN) self.rect = self.image.get_rect() self.rect.centerx = WIDTH / 2 self.rect.bottom = HEIGHT - 10 self.speedx = 0 def update(self): self.speedx = 0 keystate = pygame.key.get_pressed() if keystate[pygame.K_LEFT]: self.speedx = -8 if keystate[pygame.K_RIGHT]: self.speedx = 8 self.rect.x += self.speedx if self.rect.right > WIDTH: self.rect.right = WIDTH if self.rect.left < 0: self.rect.left = 0 class Mob(pygame.sprite.Sprite): def __init__(self): pygame.sprite.Sprite.__init__(self) self.image = pygame.Surface((30, 40)) self.image.fill(RED) self.rect = self.image.get_rect() self.rect.x = random.randrange(WIDTH - self.rect.width) self.rect.y = random.randrange(-100, -40) self.speedy = random.randrange(1, 8) self.speedx = random.randrange(-3, 3) def update(self): self.rect.x += self.speedx self.rect.y += self.speedy if self.rect.top > HEIGHT + 10 or self.rect.left < -25 or self.rect.right > WIDTH + 20: self.rect.x = random.randrange(WIDTH - self.rect.width) self.rect.y = random.randrange(-100, -40) self.speedy = random.randrange(1, 8) all_sprites = pygame.sprite.Group() mobs = pygame.sprite.Group() player = Player() all_sprites.add(player) for i in range(8): m = Mob() all_sprites.add(m) mobs.add(m) # Game loop running = True while running: # keep loop running at the right speed clock.tick(FPS) # Process input (events) for event in pygame.event.get(): # check for closing window if event.type == pygame.QUIT: running = False # Update all_sprites.update() # Draw / render screen.fill(BLACK) all_sprites.draw(screen) # *after* drawing everything, flip the display pygame.display.flip() pygame.quit()
在下一课中，将学习如何检测两个精灵何时碰到对方（碰撞）并让玩家回击怪物。
