'''
Write a program that draws, centred on the screen, a blue circle with a radius 
of 50 pixels using the writer's drawCircle function:
'''

pen.drawCircle (x, y, r, c, f)

'''
The first two arguments (`x` and `y`) specify the centre of the circle. The 
third argument is the radius of the circle. The fourth argument specifies the 
colour, and the last argument is a Boolean to specify whether the circle should
be filled or not. 

Five seconds after drawing the circle, the screen should be cleared. 
The code below shows you how to how delay (pause in milliseconds) and then 
clear the screen: 
'''

screen.pause(5000) 
screen.clear() 
screen.update() # The screen needs to be updated to see the effect of the clearing 
screen.keepwindow()