Joystick seems to be working well.  Gently pressing one side of the button seems to dim the fibers slowly as intended!  Fibers are illuminated by a 3 mm red LED.  The LED is powered by 2 AAA batteries through a resistor.  Here is how they look in the camera:

 First impression is that the button(s) can be pressed too deep on one side blocking the light on all fibers.  I will make the lid thicker to prevent this.  Also, I think I am going to turn the "X" in the joystick body 45 degrees to make it easier to read the joystick... I though having 2 fibers dim when one corner is pressed would be better but it might be the opposite.