Very simple game

game.py

from os import environ
environ['PYGAME_HIDE_SUPPORT_PROMPT'] = '1'
from pygame import Rect, init, K_LEFT, K_RIGHT, K_UP, K_DOWN, K_RETURN, K_ESCAPE, K_r, K_p, QUIT
from pygame.event import get
from pygame.font import Font
from pygame.key import get_pressed
from pygame.display import set_mode, flip
from pygame.draw import rect
from pygame.time import delay
from random import randint, choice
# from pygame.mixer import init as m_init, music
# m_init()
# music.load("bg.mp3")
# music.play(-1, 0)
init()
screen = set_mode((800, 600))
player = Rect(0, 0, 50, 50)
enemies = []
enemies_speed = []
font = Font(None, 36)
highscore = 0
game_over = True
def add_enemy():
    global enemies, enemies_speed
    enemy = Rect(0, 0, 50, 50)
    if player.left > 100:
        enemy.x = randint(0, player.left - 100)
        if enemy.right < 700:
            enemy.x = choice([enemy.x, randint(enemy.right + 50, 750)])
    else:
        enemy.x = randint(player.right + 50, 750)
    if player.top > 100:
        enemy.y = randint(0, player.top - 100)
        if enemy.bottom < 500:
            enemy.y = choice([enemy.y, randint(enemy.bottom + 50, 550)])
    else:
        enemy.y = randint(player.bottom + 50, 550)
    enemies.append(enemy)
    enemies_speed.append((choice([-1, 1]) * randint(1, 5), choice([-1, 1]) * randint(1, 5)))
def main_menu():
    global player, enemies, enemies_speed
    screen.blit(font.render(f"Press ENTER to {'play' if game_over else 'continue'}", 1, (0, 0, 255)), (100, 100))
    screen.blit(font.render("Press ESC to exit", 1, (0, 0, 255)), (120, 200))
    screen.blit(font.render("Score: " + str(len(enemies)), 1, (0, 0, 255)), (140, 300))
    screen.blit(font.render("Highscore: " + str(highscore), 1, (0, 0, 255)), (160, 400))
    flip()
    if game_over:
        player = Rect(0, 0, 50, 50)
        enemies = []
        enemies_speed = []
    while True:
        for e in get():
            if e.type == QUIT:
                exit()
        keys = get_pressed()
        if keys[K_RETURN]:
            play()
            break
        if keys[K_ESCAPE]:
            exit()
def play():
    global player, enemies, enemies_speed, highscore, game_over
    running, counter, game_over = True, 0, True
    while running:
        for e in get():
            if e.type == QUIT:
                exit()
        keys = get_pressed()
        if keys[K_LEFT]:  player.x -= 5
        if keys[K_RIGHT]: player.x += 5
        if keys[K_UP]:    player.y -= 5
        if keys[K_DOWN]:  player.y += 5
        if keys[K_r]:
            player = Rect(0, 0, 50, 50)
            enemies = []
            enemies_speed = []
        if keys[K_p]:
            running = False
            game_over = False
        if keys[K_ESCAPE]:
            exit()
        if player.bottom > 600: player.y = 0
        if player.top < 0:      player.y = 600 - player.height
        if player.right > 800:  player.x = 0
        if player.left < 0:     player.x = 800 - player.width
        screen.fill((0, 0, 0))
        for i in range(len(enemies)):
            enemies[i] = enemies[i].move(enemies_speed[i])
            if (enemies[i].left < 0 or enemies[i].right > 800) and (enemies[i].top < 0 or enemies[i].bottom > 600):
                enemies_speed[i] = (-enemies_speed[i][0], -enemies_speed[i][1])
            elif enemies[i].left < 0 or enemies[i].right > 800:
                enemies_speed[i] = (-enemies_speed[i][0], enemies_speed[i][1])
            elif enemies[i].top < 0 or enemies[i].bottom > 600:
                enemies_speed[i] = (enemies_speed[i][0], -enemies_speed[i][1])
            rect(screen, (255, 0, 0), enemies[i])
        rect(screen, (0, 255, 0), player)
        counter = (counter + 1) % 60
        if not counter: add_enemy()
        for i in range(len(enemies)):
            if enemies[i].colliderect(player):
                running = False
        screen.blit(font.render("Score: " + str(len(enemies)), 1, (0, 0, 255)), (0, 0))
        flip()
        delay((20 + 1000 * (not running)) * game_over)
    highscore = max(highscore, len(enemies))
while True:
    main_menu()