def build (self): sm = ScreenManager() sm.music = self.menu_music sm.music.play() sm.music.volume = 0.3 sm.music.loop = True sm.right_answers = NumericProperty(0) sm.wrong_answers = NumericProperty(0) sm.add_widget(StartScreen(name = 'menu')) sm.add_widget(ChooseQuiz(name = 'chooser')) sm.add_widget(PlayScreen(name = 'play')) sm.add_widget(HighScoreScreen(name = 'score')) return sm