new_contents: # Light LEDs at random and make them fade over time
  #
  # Usage:
  #
  #    led_dance(delay)
  #
  # 'delay' is the time between each new LED being turned on.
  #
  # TODO The random number generator is not great. Perhaps the accelerometer
  # or compass could be used to add entropy.
  
  import microbit
  
  def led_dance(delay):
      dots = [ [0]*5, [0]*5, [0]*5, [0]*5, [0]*5 ]
      microbit.display.set_display_mode(1)
      while True:
          dots[microbit.random(5)][microbit.random(5)] = 128
          for i in range(5):
              for j in range(5):
                  microbit.display.image.set_pixel(i, j, dots[i][j])
                  dots[i][j] = int(dots[i][j]/2)
          microbit.sleep(delay)
  
  led_dance(100)
  
subject: Add LED dance example