用pygame生成一个平面射击游戏，要求角色射击时，武器一段固定在角色中心，另一端始终指向鼠标

以下是一个用pygame生成平面射击游戏的示例代码，其中包括一个角色和一些敌人，角色可以射击并击败敌人。在角色射击时，武器会一段固定在角色中心，另一端会始终指向鼠标。

import pygame
import random

# 初始化pygame
pygame.init()

# 设置游戏窗口尺寸
screen_width = 800
screen_height = 600
screen = pygame.display.set_mode((screen_width, screen_height))
pygame.display.set_caption("Plane Shooting Game")

# 定义颜色
WHITE = (255, 255, 255)
BLACK = (0, 0, 0)
RED = (255, 0, 0)
GREEN = (0, 255, 0)
BLUE = (0, 0, 255)

# 加载角色和敌人图片
player_img = pygame.image.load("player.png")
enemy_img = pygame.image.load("enemy.png")

# 定义角色类
class Player(pygame.sprite.Sprite):
    def __init__(self, x, y):
        super().__init__()
        self.image = player_img
        self.rect = self.image.get_rect()
        self.rect.center = (x, y)
        self.weapon_length = 50
        self.weapon_angle = 0

    def update(self):
        # 更新角色位置
        self.rect.center = pygame.mouse.get_pos()

        # 更新武器角度
        mouse_x, mouse_y = pygame.mouse.get_pos()
        player_x, player_y = self.rect.center
        self.weapon_angle = -pygame.math.atan2(player_x-mouse_x, player_y-mouse_y)*180/pygame.math.pi
        self.weapon_angle %= 360

    def shoot(self):
        # 创建子弹对象
        bullet = Bullet(self.rect.centerx, self.rect.centery, self.weapon_angle)
        all_sprites.add(bullet)
        bullets.add(bullet)

# 定义敌人类
class Enemy(pygame.sprite.Sprite):
    def __init__(self):
        super().__init__()
        self.image = enemy_img
        self.rect = self.image.get_rect()
        self.rect.x = random.randrange(screen_width - self.rect.width)
        self.rect.y = random.randrange(-100, -40)
        self.speed = random.randrange(1, 4)

    def update(self):
        # 更新敌人位置
        self.rect.y += self.speed
        if self.rect.top > screen_height + 10:
            self.rect.x = random.randrange(screen_width - self.rect.width)
            self.rect.y = random.randrange(-100, -40)
            self.speed = random.randrange(1, 4)

# 定义子弹类
class Bullet(pygame.sprite.Sprite):
    def __init__(self, x, y, angle):
        super().__init__()
        self.image = pygame.Surface((10, 20))
        self.image.fill(RED)
        self.rect = self.image.get_rect()
        self.rect.center = (x, y)
        self.speed = 10
        self.angle = angle

    def update(self):
        # 更新子弹位置
        self.rect.y -= self.speed * pygame.math.sin(self.angle/180*pygame.math.pi)
        self.rect.x -= self.speed * pygame.math.cos(self.angle/180*pygame.math.pi)
        if self.rect.bottom < 0:
            self.kill()

# 创建角色对象和敌人组
player = Player(screen_width/2, screen_height/2)
all_sprites = pygame.sprite.Group()
enemies = pygame.sprite.Group()
bullets = pygame.sprite.Group()
all_sprites.add(player)

for i in range(10):
    enemy = Enemy()
    all_sprites.add(enemy)
    enemies.add(enemy)

# 定义游戏循环
running = True
clock = pygame.time.Clock()
while running:
    # 处理事件
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            running = False
        elif event.type == pygame.MOUSEBUTTONDOWN:
            if event.button == 1:
                player.shoot()

    # 更新游戏状态
    all_sprites.update()

    # 检测碰撞
    hits = pygame.sprite.groupcollide(enemies, bullets, True, True)

    for hit in hits:
        enemy = Enemy()
        all_sprites.add(enemy)
        enemies.add(enemy)

    hits = pygame.sprite.spritecollide(player, enemies, False)
    if hits:
        running = False

    # 绘制游戏界面
    screen.fill(WHITE)
    all_sprites.draw(screen)

    # 绘制武器线段
    weapon_start = player.rect.center
    weapon_end_x = player.rect.centerx + player.weapon_length * pygame.math.sin(player.weapon_angle/180*pygame.math.pi)
    weapon_end_y = player.rect.centery + player.weapon_length * pygame.math.cos(player.weapon_angle/180*pygame.math.pi)
    weapon_end = (weapon_end_x, weapon_end_y)
    pygame.draw.line(screen, BLACK, weapon_start, weapon_end, 2)

    # 刷新屏幕
    pygame.display.flip()

    # 控制游戏帧率
    clock.tick(60)

# 退出游戏
pygame.quit()