I have to wonder if they started out with higher ambitions, and it didn’t quite come together. It seems to me that the obvious cool thing to do would be to have a multi-touch user interface table (with no iPad) that can recognize the locations of the ‘prisms’ and then apply the physics to simulate the light rays. Then to make things super cool, you can mess with the physics, and mess with what constitutes a ‘prism.’
But here, the projector doesn’t know where the prisms are. The effects at the end are achieved by shining the projector across the surface of the table; basically a very expensive laser pointer.