Pygame main menu for game

I have four files: main.py, game.py, menu.py and asteroids.py. I have shown the python code for every file apart from the asteroids one which can be found at: https://github.com/araboy24/AsteroidsTut.

I watched a tutorial on how to make the game and need to add in a main menu that shows before the game starts. I have tried adding in the code to the different files to see what happens but I can't figure out what I am doing wrong.

main.py

from game import Game

g = Game()

while g.running:
    g.curr_menu.display_menu()
    g.game_loop()

game.py

import pygame
from menu import *
from asteroids import *


class Game():
    def __init__(self):
        pygame.init()
        self.running, self.playing = True, False
        self.UP_KEY, self.DOWN_KEY, self.START_KEY, self.BACK_KEY = False, False, False, False
        self.DISPLAY_W, self.DISPLAY_H = 480, 270
        self.display = pygame.Surface((self.DISPLAY_W,self.DISPLAY_H))
        self.window = pygame.display.set_mode(((self.DISPLAY_W,self.DISPLAY_H)))
        self.font_name = pygame.font.get_default_font()
        self.BLACK, self.WHITE = (0, 0, 0), (255, 255, 255)
        self.main_menu = MainMenu(self)
        self.options = OptionsMenu(self)
        self.credits = CreditsMenu(self)
        self.curr_menu = self.main_menu

    def game_loop(self):
        while self.playing:
            self.check_events()
            if self.START_KEY:
                self.playing= False
            self.display.fill(self.BLACK)
            self.draw_text('Thanks for Playing', 20, self.DISPLAY_W/2, self.DISPLAY_H/2)
            self.window.blit(self.display, (0,0))
            pygame.display.update()
            self.reset_keys()



    def check_events(self):
        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                self.running, self.playing = False, False
                self.curr_menu.run_display = False
            if event.type == pygame.KEYDOWN:
                if event.key == pygame.K_RETURN:
                    self.START_KEY = True
                if event.key == pygame.K_BACKSPACE:
                    self.BACK_KEY = True
                if event.key == pygame.K_DOWN:
                    self.DOWN_KEY = True
                if event.key == pygame.K_UP:
                    self.UP_KEY = True

    def reset_keys(self):
        self.UP_KEY, self.DOWN_KEY, self.START_KEY, self.BACK_KEY = False, False, False, False

    def draw_text(self, text, size, x, y ):
        font = pygame.font.Font(self.font_name,size)
        text_surface = font.render(text, True, self.WHITE)
        text_rect = text_surface.get_rect()
        text_rect.center = (x,y)
        self.display.blit(text_surface,text_rect)

menu.py

import pygame

class Menu():
    def __init__(self, game):
        self.game = game
        self.mid_w, self.mid_h = self.game.DISPLAY_W / 2, self.game.DISPLAY_H / 2
        self.run_display = True
        self.cursor_rect = pygame.Rect(0, 0, 20, 20)
        self.offset = - 100

    def draw_cursor(self):
        self.game.draw_text('*', 15, self.cursor_rect.x, self.cursor_rect.y)

    def blit_screen(self):
        self.game.window.blit(self.game.display, (0, 0))
        pygame.display.update()
        self.game.reset_keys()

class MainMenu(Menu):
    def __init__(self, game):
        Menu.__init__(self, game)
        self.state = "Start"
        self.startx, self.starty = self.mid_w, self.mid_h + 30
        self.optionsx, self.optionsy = self.mid_w, self.mid_h + 50
        self.creditsx, self.creditsy = self.mid_w, self.mid_h + 70
        self.cursor_rect.midtop = (self.startx + self.offset, self.starty)

    def display_menu(self):
        self.run_display = True
        while self.run_display:
            self.game.check_events()
            self.check_input()
            self.game.display.fill(self.game.BLACK)
            self.game.draw_text('Main Menu', 20, self.game.DISPLAY_W / 2, self.game.DISPLAY_H 
/ 2 - 20)
            self.game.draw_text("Start Game", 20, self.startx, self.starty)
            self.game.draw_text("Options", 20, self.optionsx, self.optionsy)
            self.game.draw_text("Credits", 20, self.creditsx, self.creditsy)
            self.draw_cursor()
            self.blit_screen()


    def move_cursor(self):
        if self.game.DOWN_KEY:
            if self.state == 'Start':
                self.cursor_rect.midtop = (self.optionsx + self.offset, self.optionsy)
                self.state = 'Options'
            elif self.state == 'Options':
                self.cursor_rect.midtop = (self.creditsx + self.offset, self.creditsy)
                self.state = 'Credits'
            elif self.state == 'Credits':
                self.cursor_rect.midtop = (self.startx + self.offset, self.starty)
                self.state = 'Start'
        elif self.game.UP_KEY:
            if self.state == 'Start':
                self.cursor_rect.midtop = (self.creditsx + self.offset, self.creditsy)
                self.state = 'Credits'
            elif self.state == 'Options':
                self.cursor_rect.midtop = (self.startx + self.offset, self.starty)
                self.state = 'Start'
            elif self.state == 'Credits':
                self.cursor_rect.midtop = (self.optionsx + self.offset, self.optionsy)
                self.state = 'Options'

    def check_input(self):
        self.move_cursor()
        if self.game.START_KEY:
            if self.state == 'Start':
                self.game.playing = True
            elif self.state == 'Options':
                self.game.curr_menu = self.game.options
            elif self.state == 'Credits':
                self.game.curr_menu = self.game.credits
            self.run_display = False

class OptionsMenu(Menu):
    def __init__(self, game):
        Menu.__init__(self, game)
        self.state = 'Volume'
        self.volx, self.voly = self.mid_w, self.mid_h + 20
        self.controlsx, self.controlsy = self.mid_w, self.mid_h + 40
        self.cursor_rect.midtop = (self.volx + self.offset, self.voly)

    def display_menu(self):
        self.run_display = True
        while self.run_display:
            self.game.check_events()
            self.check_input()
            self.game.display.fill((0, 0, 0))
            self.game.draw_text('Options', 20, self.game.DISPLAY_W / 2, self.game.DISPLAY_H / 
2 - 30)
            self.game.draw_text("Volume", 15, self.volx, self.voly)
            self.game.draw_text("Controls", 15, self.controlsx, self.controlsy)
            self.draw_cursor()
            self.blit_screen()

    def check_input(self):
        if self.game.BACK_KEY:
            self.game.curr_menu = self.game.main_menu
            self.run_display = False
        elif self.game.UP_KEY or self.game.DOWN_KEY:
            if self.state == 'Volume':
                self.state = 'Controls'
                self.cursor_rect.midtop = (self.controlsx + self.offset, self.controlsy)
            elif self.state == 'Controls':
                self.state = 'Volume'
                self.cursor_rect.midtop = (self.volx + self.offset, self.voly)
        elif self.game.START_KEY:
            # TO-DO: Create a Volume Menu and a Controls Menu
            pass

class CreditsMenu(Menu):
    def __init__(self, game):
        Menu.__init__(self, game)

    def display_menu(self):
        self.run_display = True
        while self.run_display:
            self.game.check_events()
            if self.game.START_KEY or self.game.BACK_KEY:
                self.game.curr_menu = self.game.main_menu
                self.run_display = False
            self.game.display.fill(self.game.BLACK)
            self.game.draw_text('Credits', 20, self.game.DISPLAY_W / 2, self.game.DISPLAY_H / 
2 - 20)
            self.game.draw_text('Made by me', 15, self.game.DISPLAY_W / 2, self.game.DISPLAY_H 
/ 2 + 10)
            self.blit_screen()

source https://stackoverflow.com/questions/70931564/pygame-main-menu-for-game