Ya i was honestly just trying to figure it out.I made a coffee table with motion sensor that when ever u touch the table it goes from privacy black to clear.I went to school for 4.5 years for computer and tech repair. I think they either use this material that is like mercury can think of the name of it. Mirrors the image then the projection would just invert it back to the right direction.
ps i didnt mean it as an EASY concept its just one i think i can do with time and a lil help from a few ppl i know that work in software programming. You would be surprised what I.T students can do