@@ -30,7 +30,7 @@ If you speak Chinese, you can watch my [Youtube channel](https://www.youtube.com
 
 # Donation
 
-*If this does help you, please considering donation to support me to make better tutorials*
+*If this does help you, please consider donating to support me for better tutorials. Any contribution is greatly appreciated!*
 
 <div >
   <a href="https://www.paypal.com/cgi-bin/webscr?cmd=_donations&amp;business=morvanzhou%40gmail%2ecom&amp;lc=C2&amp;item_name=MorvanPython&amp;currency_code=AUD&amp;bn=PP%2dDonationsBF%3abtn_donateCC_LG%2egif%3aNonHosted">
 
@@ -100,7 +100,6 @@ def _get_state(self):
                           ]), t_arms[-2:]
 
     def _r_func(self, distance):
-        """Headway and distance based reward system"""
         t = 50
         abs_distance = np.sqrt(np.sum(np.square(distance)))
         r = -abs_distance/200