我想把分数设置为10，当一个按钮被点击，但它不工作。 当单击第一个按钮时，得分应从0增加到10，当使用kivy按下第二个按钮时，得分应从10增加到20

import kivy
from kivy.app import App
from kivy.uix.floatlayout import Floatlayout
from kivy.uix.widget import Widget
from kivy.uix.button import Button
from kivy.label import Label 


class LandingScreen(FloatLayout):
    def __init__(self, **kwargs):
        super(LandingScreen, self).__init__(**kwargs)

         self.score=0

        # put whatever pos_hint value you want.          
        self.add_widget(Label(text='SCORE: ' + str(score), size_hint=(0.5, 0.5)))
        self.btn1=Button(text='button1 ', size_hint=(0.5, 0.5), 
        on_press=self.click_b1))
        self.btn2=Button(text='button2', size_hint=(0.5, 0.5), 
        on_press=self.click_b2))


            
        self.add_widget(self.btn1)
        self.add_widget(self.btn2)

        def click_b1(self, instance):
             
             score +=10
        def click_b2(self, instance):
             score += 10
       
class SplashApp(App):
    def build(self):
        return LandingScreen()

if __name__ == '__main__':
    SplashApp().run()