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
