Что не так в коде? Нужно чтобы мобы вылетали справа и летели налево, а они летят сверху вниз и глючат, как исправить? (Class Mob нужно изменить)

import pygame
import random

WIDTH = 1920
HEIGHT = 820
FPS = 60
x = 50
y = 380

WHITE = (255, 255, 255)
BLACK = (0, 0, 0)
RED = (255, 0, 0)
GREEN = (0, 255, 0)
BLUE = (0, 0, 255)
YELLOW = (255, 255, 0)

pygame.init()
pygame.mixer.init()
screen = pygame.display.set_mode((WIDTH, HEIGHT))
pygame.display.set_caption("Победи демонов!")
clock = pygame.time.Clock()

monster1_image = pygame.image.load('monster1.gif')
monster1_image = pygame.transform.scale(monster1_image, (350, 350))

class Player(pygame.sprite.Sprite):
    def __init__(self):
        pygame.sprite.Sprite.__init__(self)
        self.image = pygame.image.load('player.png').convert_alpha()
        self.rect = self.image.get_rect()
        self.rect.centerx = WIDTH / 5
        self.rect.bottom = HEIGHT - 5
        self.speedx = 0

    def update(self):
        self.speedx = 0
        keys = pygame.key.get_pressed()
        if keys[pygame.K_a]:
            self.speedx = -8
        if keys[pygame.K_d]:
            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

    def shoot(self):
        bullet = Bullet(self.rect.centerx, self.rect.left)
        player_group.add(bullet)
        bullets.add(bullet)

class Mob(pygame.sprite.Sprite):
    def __init__(self):
        pygame.sprite.Sprite.__init__(self)
        self.image = monster1_image
        self.rect = self.image.get_rect()
        self.rect.x = random.randrange(2000, 3000)
        self.rect.y = random.randrange(-1920, -50)
        self.speedy = random.randrange(1, 2)
        self.speedx = random.randrange(2, 3)

    def update(self):
        self.rect.x += self.speedx
        self.rect.y += self.speedy
        if self.rect.right > HEIGHT + 10 or self.rect.left < -25 or self.rect.right > WIDTH + 20:
            self.rect.x = random.randrange(1920, 3000)
            self.rect.y = random.randrange(-1920, -50)
            self.speedy = random.randrange(1, 8)

class Bullet(pygame.sprite.Sprite):
    def __init__(self, x, y):
        pygame.sprite.Sprite.__init__(self)
        self.image = pygame.Surface((10, 20))
        self.image.fill(YELLOW)
        self.rect = self.image.get_rect()
        self.rect.bottom = y
        self.rect.centerx = x
        self.speedy = -10

    def update(self):
        self.rect.y += self.speedy
        if self.rect.bottom < 0:
            self.kill()

player_group = pygame.sprite.Group()
mobs = pygame.sprite.Group()
bullets = pygame.sprite.Group()
player = Player()
player_group.add(player)
for i in range(2):
    m = Mob()
    player_group.add(m)
    mobs.add(m)

swag = True
while swag:
    clock.tick(FPS)
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            swag = False
        elif event.type == pygame.KEYDOWN:
            if event.key == pygame.K_SPACE:
                player.shoot()

    player_group.update()

    hits = pygame.sprite.groupcollide(mobs, bullets, True, True)
    for hit in hits:
        m = Mob()
        player_group.add(m)
        mobs.add(m)

    hits = pygame.sprite.spritecollide(player, mobs, False)
    if hits:
        swag = False

    screen.fill(BLACK)
    player_group.draw(screen)
    pygame.display.update()

pygame.quit()

Весь код всё-таки дал, но там нужно сделать изменения в Class Mob, чтобы он начал справа на лево лететь