'''
Exercise A:
Write a program, using the writer tool, that draws a red circle with a radius 
of 25 pixels at a random position on the graphical window. Each time you 
re-run the program, the position should be different (random). Make sure the 
circle always fits completely within the screen.

Exercise B:
Extend your code from exercise A such that it draws 100 red circles with 
radiuses of 5 pixels at random positions on the graphical window. Your program 
should incorporate: 
- Lists for the `x` and `y` coordinates. 
- A loop to fill the list with random coordinates.
- A second loop to draw the circles.

Exercise C:
Extend your code from exercise B such that it draws a 100 red circles. Every 
100 ms a new circle should be added at a random position within the graphical 
window. 

Exercise D:
Extend your code from exercise C such that it draws 100 red circles one by one 
with 100 ms intervals at random positions on the graphical window, but now each 
time when a new circle is drawn, all previous circles should move one pixel down. 

You can use a nested for loop: the outer loop determines the number of circles 
to be drawn and in the inner loop those circles will be drawn. 
'''