At first he glued sheets of styrofoam.
-cut cylinder shape;
-cut pieces of the cylinder;
-made the form of a sphere;
-divided it in half;
-cut inside place for micro-controller;
-soldered circuit of LED diodes;
-put bottom side of them inside the sphere;
-set up plastic mirror pieces on the surface;
-set up micro-controller, button and battery supply.
At last he filled surface with silicon.
So you can see how in works=)