请问老师我的子弹为什么不会消失
import pygame, time, random
_display = pygame.display
COLOR_BLACK = pygame.Color(0, 0, 0)
COLOR_WHITE = pygame.Color(255, 0, 0)
class MainGame():
    # 开始游戏方法
    window = None
    Screen_Height = 500
    Screen_Width = 800
    My_tank = None
    Tank_P1 = None
    Enemytanklist = []
    Enemytank_count = 5
    bulluetlist = []
    def startGame(self):
        # 初始化
        pygame.display.init()
        # 设置窗口大小
        MainGame.window = pygame.display.set_mode([MainGame.Screen_Width, MainGame.Screen_Height])
        # 设置标题
        _display.set_caption('坦克大战1.03')
        # 初始化我方坦克
        MainGame.Tank_P1 = Tank(400, 250)
        # 初始化敌方坦克
        self.createEnemytank()
        while True:
            # 延时
            time.sleep(0.02)
            # 设置颜色
            MainGame.window.fill(COLOR_BLACK)
            # 获取事件
            self.getevent()
            # 显示文本敌方坦克数量
            MainGame.window.blit(self.getTextSurface('剩余敌方坦克{}辆'.format(MainGame.Enemytank_count)), (5, 5))
            # 我方坦克展示
            MainGame.Tank_P1.show_tank()
            # 循环遍历敌方坦克列表,敌方坦克展示
            MainGame.blitEnemytank(self)
            # 子弹展示
            MainGame.blitMyBulluet(self)
            # 是否停止
            if not MainGame.Tank_P1.stop == True:
                MainGame.Tank_P1.move()
            _display.update()
    def endGame(self):
        print('游戏结束')
        exit()
    def getevent(self):
        eventlist = pygame.event.get()
        for event in eventlist:
            if event.type == pygame.QUIT:
                self.endGame()
            if event.type == pygame.KEYDOWN:
                if event.key == pygame.K_LEFT:
                    print('按下左键,坦克向左移动')
                    MainGame.Tank_P1.direction = 'L'
                    MainGame.Tank_P1.stop = False
                    # 调用移动方法
                    # MainGame.Tank_P1.move()
                elif event.key == pygame.K_RIGHT:
                    print('按下右键,坦克向右移动')
                    MainGame.Tank_P1.direction = 'R'
                    MainGame.Tank_P1.stop = False
                    # 调用移动方法
                    # MainGame.Tank_P1.move()
                elif event.key == pygame.K_UP:
                    print('按下上键,坦克向上移动')
                    MainGame.Tank_P1.direction = 'U'
                    MainGame.Tank_P1.stop = False
                    # 调用移动方法
                    # MainGame.Tank_P1.move()
                elif event.key == pygame.K_DOWN:
                    print('按下下键,坦克向下移动')
                    MainGame.Tank_P1.direction = 'D'
                    MainGame.Tank_P1.stop = False
                    # 调用移动方法
                    # MainGame.Tank_P1.move()
                elif event.key == pygame.K_SPACE:
                    print('biubiubiu')
                    m = Bulluet(MainGame.Tank_P1)
                    MainGame.bulluetlist.append(m)
            if event.type == pygame.KEYUP:
                if event.key == pygame.K_UP or pygame.K_LEFT or pygame.K_RIGHT or pygame.KEYDOWN:
                    MainGame.Tank_P1.stop = True
    def getTextSurface(self, text):
        # 初始化字体
        pygame.font.init()
        # 选中合适的字体
        font = pygame.font.SysFont('kaiti', 18)
        textsurface = font.render(text, True, COLOR_WHITE)
        return textsurface
    # 创建敌方坦克的方法
    def createEnemytank(self):
        top = 100
        for i in range(MainGame.Enemytank_count):
            left = random.randint(0, 600)
            speed = random.randint(3, 6)
            enemy = Enemytank(left, top, speed)
            MainGame.Enemytanklist.append(enemy)
        # 循环遍历敌方坦克列表,敌方坦克展示
    def blitEnemytank(self):
        for Enemytank in MainGame.Enemytanklist:
            Enemytank.show_tank()
            Enemytank.randMove()
    def blitMyBulluet(self):
        for mybulluet in MainGame.bulluetlist:
            if mybulluet.alive:
                mybulluet.show_bulluet()
                mybulluet.move()
            else:
                MainGame.bulluetlist.remove(mybulluet)
class Tank():
    def __init__(self, left, top):
        self.images = {
            'U': pygame.image.load('image/p1tankU.gif'),
            'D': pygame.image.load('image/p1tankD.gif'),
            'L': pygame.image.load('image/p1tankL.gif'),
            'R': pygame.image.load('image/p1tankR.gif'),
        }
        self.direction = 'U'
        self.image = self.images[self.direction]
        # 坦克所在的区域
        self.rect = self.image.get_rect()
        self.rect.left = left
        self.rect.top = top
        self.speed = 10
        self.stop = True
    # 坦克移动
    def move(self):
        # 坦克移动的方向
        if self.direction == 'L':
            if self.rect.left > 0:
                self.rect.left -= self.speed
        elif self.direction == 'R':
            if self.rect.left + self.rect.height < MainGame.Screen_Width:
                self.rect.left += self.speed
        elif self.direction == 'U':
            if self.rect.top > 0:
                self.rect.top -= self.speed
        elif self.direction == 'D':
            if self.rect.top + self.rect.height < MainGame.Screen_Height:
                self.rect.top += self.speed
    # 坦克射击
    def shoot(self):
        pass
    # 坦克展示
    def show_tank(self):
        self.image = self.images[self.direction]
        MainGame.window.blit(self.image, self.rect)
    # 碰撞墙壁
    def hitWalls(self):
        pass
class Mytank(Tank):
    def __init__(self):
        pass
    # 碰撞敌方坦克的方法
    def hitEnemytank(self):
        pass
class Enemytank(Tank):
    def __init__(self, left, top, speed):
        self.images = {
            'U': pygame.image.load('image/enemy1U.gif'),
            'D': pygame.image.load('image/enemy1D.gif'),
            'L': pygame.image.load('image/enemy1L.gif'),
            'R': pygame.image.load('image/enemy1R.gif')
        }
        self.direction = 'U'
        self.image = self.images[self.direction]
        self.rect = self.image.get_rect()
        self.rect.left = left
        self.rect.top = top
        self.direction = self.randDirection()
        self.speed = speed
        self.step = 0
    # 碰撞我方坦克的方法
    def hitMytank(self):
        pass
    # 敌方坦克随机方向的方法
    def randDirection(self):
        num = random.randint(1, 4)
        if num == 1:
            return 'U'
        if num == 2:
            return 'D'
        if num == 3:
            return 'R'
        if num == 4:
            return 'L'
    # 随机移动的方法
    def randMove(self):
        if self.step < 0:
            self.direction = Enemytank.randDirection(self)
            self.step = 20
        else:
            self.step -= 1
            self.move()
class Bulluet():
    def __init__(self, tank):
        # 加载图片
        self.image = pygame.image.load('image/enemymissile.gif')
        # 定义方向
        self.direction = tank.direction
        # 位置
        self.rect = self.image.get_rect()
        if self.direction == 'U':
            self.rect.left = tank.rect.left + tank.rect.width / 2 - self.rect.width / 2
            self.rect.top = tank.rect.top - self.rect.height
        elif self.direction == 'D':
            self.rect.left = tank.rect.left + tank.rect.width / 2 - self.rect.width / 2
            self.rect.top = tank.rect.top + tank.rect.height
        elif self.direction == 'L':
            self.rect.left = tank.rect.left - self.rect.width / 2 - self.rect.width / 2
            self.rect.top = tank.rect.top + tank.rect.width / 2 - self.rect.width / 2
        elif self.direction == 'R':
            self.rect.left = tank.rect.left + tank.rect.width
            self.rect.top = tank.rect.top + tank.rect.width / 2 - self.rect.width / 2
            # 速度
        self.speed = 7
        # 用来记录子弹是否活着
        self.alive = True
    # 子弹移动
    def move(self):
        if self.direction == 'L':
            if self.rect.left > 0:
                self.rect.left -= self.speed
            else:
                self.alive == False
        elif self.direction == 'R':
            if self.rect.left + self.rect.height < MainGame.Screen_Width:
                self.rect.left += self.speed
            else:
                self.alive == False
        elif self.direction == 'U':
            if self.rect.top > 0:
                self.rect.top -= self.speed
            else:
                self.alive == False
        elif self.direction == 'D':
            if self.rect.top + self.rect.height < MainGame.Screen_Height:
                self.rect.top += self.speed
            else:
                self.alive == False
    # 子弹展示
    def show_bulluet(self):
        MainGame.window.blit(self.image, self.rect)
    # 子弹碰撞坦克方法
    def hitTank(self):
        pass
    # 子弹碰撞墙壁的方法
    def hitWalls(self):
        pass
    # 子弹碰撞窗口的方法
    '''def hitwindow(self):
        if not self.rect.left == 0 or self.rect.left + self.rect.height == MainGame.Screen_Width \
                or self.rect.top == 0 or self.rect.top + self.rect.height == MainGame.Screen_Height:
            self.alive = True
'''
class Wall():
    def __init__(self):
        pass
    # 墙壁展示
    def show_wall(self):
        pass
class Explode():
    def __init__(self):
        pass
    # 展示爆炸
    def show_explode(self):
        pass
class Music():
    def __init__(self):
        pass
    # 展示音乐
    def playmusic(self):
        pass
if __name__ == '__main__':
    MainGame().startGame()