title: Newbie at Kivy trying to create stopwatch
body: <p>I'm attempting to create a stopwatch in Kivy. I've completed a skeleton on Sublime Text 3 (as shown in the code below). When I run the code on Sublime Text, a window opens, but Python crashes in 4.1s.</p>
  
  <p>Here is the code in question:</p>
  
  <pre><code>import kivy
  
  from kivy.app import App
  
  from kivy.uix.gridlayout import GridLayout
  from kivy.uix.boxlayout import BoxLayout
  from kivy.uix.label import Label
  from kivy.clock import Clock
  from kivy.properties import NumericProperty
  
  from kivy.lang import Builder
  
  import time
  
  class CrudeTimerGrid(GridLayout):
      # Initialise timer with input start time
      def __init__(self,start_time):
          time = NumericProperty(start_time)
  
      def tick(self):
          if self.time &gt; 0:
              self.time -= 1
          else:
              pass
  
      def start(self):
          Clock.schedule_interval(self.tick,1)
  
      def pause(self):
          Clock.unschedule()
  
      # incomplete code
      def reset(self):
          pass
  
  
  class CrudeTimerApp(App):
      def build(self):
          # Testing timer by initialising timer with 20 seconds
          return CrudeTimerGrid(20)
  
  Builder.load_string('''
  &lt;CrudeTimerGrid&gt;
      id: timer
      rows: 2
      # insert formatting here
  
      BoxLayout:
          Label:
              text: timer.time
  
      BoxLayout:
  
          Button:
              text: "Start"
              on_press: timer.start()
  
          Button:
              text: "Pause"
              on_press: timer.pause()
  
          Button:
              text: "Reset"
              on_press: timer.reset()
  ''')
  
  CrudeTimerApp().run()
  </code></pre>
  
  <p>Newbie at StackOverflow too, so please let me know if any other info is needed. Thanks for your help!</p>