new_contents: from pymouse import PyMouse
  import time
  # This script demonstrates the possibility to use a mouse as an unbound sensor.
  # To do that the cursor position is brought back to the middle of the screen at each step, and the distance moved by the mouse are integrated
  # This script is intended to be used with a second external mouse.
  # This can be achieved using MPX, and inverting the laptop mouse and externa mouse.
  # Warning: it may be difficult to stop this script with the mouse, so be sure you are able to do it with keyboard command!
  cursor = PyMouse()
  x = 0
  y = 0
  screen_size = cursor.screen_size()
  cursor.move(screen_size[0]/2, screen_size[1]/2)
  while True:
    p = cursor.position()
    x = x + p[0] - screen_size[0]/2
    y = y + p[1] - screen_size[1]/2
    print x, y, p[0] - s[0]/2, p[1] - s[1]/2
    cursor.move(screen_size[0]/2, screen_size[1]/	2)
    time.sleep(0.01)
    
  
subject: Add a test to check if an optical mouse can be used as a course sensor