It is no secret that one can build all kinds of fun things with LEGO pieces. This Ultimate Useless LEGO Machine from jkbrickworks is quite interesting though. It has a black box and robot hand that coordinate their behaviors via Bluetooth. The black box robot and the hand robot keep turning the switch on and off.
The robot inside the box responds to the switch being turned off using a light sensor. It tells the hand robot what to do and always knows what’s going on. Pretty fun project if you ask us.