Pygame SceneManager

import pygame
import os

class Scene:
    # SceneManager Interface
    def scene_draw(self, surface):
        self.on_draw(surface)

    def scene_drop(self):
        self.on_drop()

    def scene_event(self):
        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                self.on_quit()
            else:
                self.on_event(event)

    def scene_focus(self, *args, **kwargs):
        self.on_focus(*args, **kwargs)

    def scene_new(self,*args, **kwargs):
        self.on_new(*args, **kwargs)

    def scene_update(self, delta):
        self.on_update(delta)

    def flip(self, scene, *args, **kwargs):
        SceneManager.flip(scene, *args, **kwargs)

    def flip_new(self, scene, *args, **kwargs):
        SceneManager.flip_new(scene, *args, **kwargs)

    def on_quit(self):
        SceneManager.quit()

    # Scene Interface
    def on_draw(self, surface): pass
    def on_drop(self): pass
    def on_event(self, event): pass
    def on_focus(self): pass
    def on_new(self): pass
    def on_update(self, delta): pass

class SceneManager:
    @classmethod
    def create(cls, title, width, height, center=False):
        if center is True:
            os.environ['SDL_VIDEO_CENTERED'] = '1'
        elif center:
            os.environ['SDL_VIDEO_WINDOW_POS'] = '{0}, {1}'.format(*center)

        # Basic pygame setup
        pygame.display.set_caption(title)
        cls.surface = pygame.display.set_mode((width, height))
        cls.rect = cls.surface.get_rect()
        cls.clock = pygame.time.Clock()
        cls.running = False
        cls.delta = 0
        cls.fps = 60

        # Scene handling
        cls._scene = Scene()
        cls.scenes = {}

        cls.extension = []

    @classmethod
    def add_scene(cls, scene, name=None):
        if name is None:
            name = scene.__class__.__name__

        cls.scenes[name] = scene

    @classmethod
    def _flip(cls, scene):
        cls._scene.scene_drop()
        if isinstance(scene, Scene):
            cls._scene = scene
        else:
            # String: Load live scene
            cls._scene = cls.scenes[scene]

    @classmethod
    def flip(cls, scene, *args, **kwargs):
        cls._flip(scene)
        cls._scene.scene_focus(*args, **kwargs)

    @classmethod
    def flip_new(cls, scene, *args, **kwargs):
        cls._flip(scene)
        cls._scene.scene_new(*args, **kwargs)

    @classmethod
    def mainloop(cls):
        cls.running = True
        while cls.running:
            cls._scene.scene_event()
            cls._scene.scene_update(cls.delta)
            cls._scene.scene_draw(cls.surface)
            for extension in cls.extension:
                extension(cls)

            pygame.display.flip()
            cls.delta = cls.clock.tick(cls.fps)

    @classmethod
    def quit(cls):
        cls.running = False