Menu/scene example using pygame

menu_scene_game.py

"""
Sample game showing a pattern for rendering scenes and menus. This was written
for the blog entry at holdenrehg.github.io/catchergames/2021/06/22/menus-and-scenes.html

Requirements for running:
    python3.8
    pygame==2.*

@author github.com/holdenrehg
"""

import abc
import traceback
import pygame


# ------------------------------------------------------------------------------
# Globals
# ------------------------------------------------------------------------------


current_game = None


# ------------------------------------------------------------------------------
# The Engine
# ------------------------------------------------------------------------------


class Game:
    def __init__(self):
        self.clock = pygame.time.Clock()
        self.next_scene = None
        self.screen = pygame.display.set_mode((600, 400))


class Scene(abc.ABC):
    running = True

    @abc.abstractmethod
    def play(self):
        ...

    def run(self):
        self.running = True

        while self.running:
            current_game.screen.fill((0, 0, 0))

            for event in pygame.event.get():
                if event.type == pygame.QUIT:
                    self.quit()

            try:
                self.play()
            except Exception as e:
                traceback.print_exc(e)
                self.quit()

            current_game.clock.tick(60)  # frames per second

            pygame.display.flip()  # render the display

    def quit(self):
        self.running = False


# ------------------------------------------------------------------------------
# Scene's
# ------------------------------------------------------------------------------


class MainMenuScene(Scene):
    def __init__(self):
        self.frames = 0

    def play(self):
        """
        Count down from 5 to 0, and once the timer hits 0 we start the game.
        """
        self.frames += 1
        countdown = max(5 - round(self.frames / 60), 0)

        if countdown > 0:
            current_game.screen.blit(
                pygame.font.SysFont(None, 80).render(
                    f"Game starting in {countdown}", False, (255, 255, 255)
                ),
                (5, 5),
            )
        else:
            self.quit()
            current_game.next_scene = GameplayScene()


class GameplayScene(Scene):
    def play(self):
        current_game.screen.blit(
            pygame.font.SysFont(None, 60).render(
                "Welcome to the game.", False, (255, 255, 255)
            ),
            (5, 5),
        )


# ------------------------------------------------------------------------------
# Main
# ------------------------------------------------------------------------------


def main():
    pygame.init()
    pygame.display.init()
    pygame.mixer.init()

    global current_game
    current_game = Game()
    current_game.next_scene = MainMenuScene()

    while current_game.next_scene:
        next_scene = current_game.next_scene
        current_game.next_scene = None
        next_scene.run()

    pygame.quit()
    raise SystemExit


main()