Completed. Added spinner for sides instead of checkbox/radio buttons.

Also added progress bar so it looks a lil nicer.

main.py

@@ -28,7 +28,13 @@ class OrderApp(App):
             self.total_cost = 0
             print('Reset')
 
-    #def fires(self,):
+    def spinner_activated(self,value):
+        if value == "Fries":
+            self.total_cost += 3
+        elif value == "Onion Ring":
+            self.total_cost += 2
+        else:
+            self.total_cost += 1
 
 
 if __name__ == '__main__':

order.kv

@@ -40,9 +40,17 @@ BoxLayout:
         BoxLayout:
             orientation: 'horizontal'
             Label:
-                text: 'Fries?'
-                font_size: sp(26)
-            CheckBox:
+                text: 'Pick sides: '
+                size_hint: (None, 1.0)
+                size: self.texture_size
+                padding: (sp(12), 0)
+
+            Spinner:
+                id: spinner1
+                text: "Sides"
+                values: ["Fries","Onion Rings","Pickles"]
+                on_text: app.spinner_activated(spinner1.text)
+