I am building this prop as a birthday gift for my daughter. I am using an Arduino Pro Mini for the brain. All the electronics are behind the board, the components on the front, other than the toggle switch are dummies. My question is, to all the electronics people on the board is, does anyone know what the piece in the red circle is? I have identified and installed all the other parts. I have wired up the Arduino behind and all is working well. All that is stopping me from being done is to find that ONE component! The birthday is approaching, if anyone knows what that thing is, I would appreciate the help SO MUCH.