Add backbutton

main.py

@@ -43,6 +43,14 @@ class SingleBridgeScreen(Screen):
                 size_hint=(1, 0.1),
                 on_press=lambda button: self.press_button(button, group))
             self.layout.add_widget(button)
+        backbutton = Button(
+            text="Back",
+            size_hint=(1, 0.1),
+            on_press=lambda button: self.press_back_button(button, "back"))
+        self.layout.add_widget(backbutton)
+
+    def press_back_button(self, button, group):
+        self.sm.current = "bridge_screen"
 
     def press_button(self, light, button):
         print(light)