With reference to the Challenge problem for changing colours. I concluded that it was easy enough to use acceleration data that was being sampled and test their values against zero in order to set the colour values. This appeared to work correctly. However after having studied many distance courses mainly with the Open University here in UK I am aware that advice given in questions usually leads a student to a more efficient answer. I looked through the documentation and could not understand where I might have got a more efficient solution. What did i miss ?