It shows you how to build a muscle-controlled repulsor that functions just like Stark's does in the movies. When you squeeze your fist, sensors on a forearm sleeve detect your arm muscle flexing which triggers the repulsor's LEDs coming to life and a charging sound effect. And when you release your fist, it triggers a firing sound effect. You're even greeted by J.A.R.V.I.S. when you power the whole thing up, and while you don't quite need Tony Stark's technical expertise to put the whole thing together, it probably wouldn't hurt.