Pygame Diablo Like Menu

# Simple Menu Example. Still can be improved.

import os
import pygame
import itertools
from pygame.sprite import Sprite, Group

class Scene:
    def on_draw(self, surface): pass
    def on_event(self, event): pass
    def on_update(self, delta): pass

class Manager:
    def __init__(self, caption, width, height, center=True):
        if center:
            os.environ['SDL_VIDEO_CENTERED'] = '1'

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

        # Scene Interface
        self.scene = Scene()

    def mainloop(self):
        self.running = True
        while self.running:
            for event in pygame.event.get():
                self.scene.on_event(event)

            self.scene.on_update(self.delta)
            self.scene.on_draw(self.surface)
            pygame.display.flip()
            self.delta = self.clock.tick(self.fps)

    def quit(self):
        self.running = False

class MenuEntry(Sprite):
    identity = 0

    @classmethod
    def load_defaults(cls):
        cls.font = pygame.font.Font(None, 32)
        cls.color = pygame.Color('white')
        cls.highlight_color = pygame.Color('dodgerblue')

    def __init__(self, text, callback):
        Sprite.__init__(self)
        self.text = text
        self.hover = False
        self.callback = callback
        self.render()
        self.update_image()
        self.rect = self.image.get_rect()
        self.identity = MenuEntry.identity
        MenuEntry.identity += 1

    def render(self):
        color = MenuEntry.color
        highlight_color = MenuEntry.highlight_color
        self._image = MenuEntry.font.render(self.text, 1, color)
        self._hover = MenuEntry.font.render(self.text, 1, highlight_color)

    def on_mousemotion(self, event):
        self.hover = self.rect.collidepoint(event.pos)
        self.update_image()

    def on_mousebuttondown(self, event):
        if self.hover:
            if event.button == 1:
                self.callback()

    def update_image(self):
        if self.hover:
            self.image = self._hover
        else:
            self.image = self._image

class MenuScene(Scene):
    def __init__(self, manager):
        self.menu = Group(
            MenuEntry("Resume Game", self.on_resume_game),
            MenuEntry("Goto Title Screen", self.on_goto_title),
            MenuEntry("Exit Program", self.on_exit)
        )

        centerx = manager.rect.centerx
        y = itertools.count(50, 40)
        for sprite in self.menu:
            sprite.rect.centerx = centerx
            sprite.rect.y = next(y)

        self.manager = manager
        self.select = 0
        self.on_select()

    def on_draw(self, surface):
        self.menu.draw(surface)

    def on_event(self, event):
        if event.type == pygame.QUIT:
            self.manager.quit()
        elif event.type == pygame.KEYDOWN:
            if event.key == pygame.K_DOWN:
                self.select = (self.select + 1) % len(self.menu)
                self.on_select()
            elif event.key == pygame.K_UP:
                self.select = (self.select - 1) % len(self.menu)
                self.on_select()
            elif event.key == pygame.K_RETURN:
                for sprite in self.menu:
                    if sprite.identity == self.select:
                        sprite.callback()
        elif event.type == pygame.MOUSEMOTION:
            for sprite in self.menu:
                sprite.on_mousemotion(event)
                if sprite.hover:
                    self.select = sprite.identity
                    self.on_select()

        elif event.type == pygame.MOUSEBUTTONDOWN:
            for sprite in self.menu:
                sprite.on_mousebuttondown(event)

    def on_exit(self):
        self.manager.quit()

    def on_goto_title(self):
        print("going to title screen")

    def on_resume_game(self):
        print("resuming game")

    def on_select(self):
        for sprite in self.menu:
            sprite.hover = sprite.identity == self.select
            sprite.update_image()

def main():
    pygame.init()
    manager = Manager("Menu Example", 800, 600)
    MenuEntry.load_defaults()
    manager.scene = MenuScene(manager)
    manager.mainloop()

main()