from kivy.app import App
from kivy.lang import Builder
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.button import Button
from kivy.uix.label import Label

Builder.load_string('''
<CyberLabel>:
    text_size: self.size
    halign: 'center'
    valign: 'middle'
    pos_hint: {'center_y': 0.5}
<CyberBox>:
    orientation: 'horizontal'
    padding: 50
    size_hint_y: None
    height: 70
    canvas.before:
        Color:
            rgba: 1, 1, 1, 1
        Line:
            width: 1
            rectangle: self.x, self.y, self.width, self.height
''')


class CyberBox(BoxLayout):
    pass


class CyberLabel(Label):
    pass


class MainBox(BoxLayout):
    def __init__(self, **kwargs):
        self.orientation = 'vertical'
        super().__init__(**kwargs)
        box = CyberBox()
        box.add_widget(CyberLabel(text='a'))
        box.add_widget(CyberLabel(text='b'))
        button = Button(text='X', size_hint_x=None, width=100, pos_hint={'center_y': 0.5})
        button.bind(on_press=lambda _: print(_))
        box.add_widget(button)
        self.add_widget(box)


class MainApp(App):
    def build(self):
        return MainBox()


main = MainApp()
main.run()