We turned a MacBook into a touchscreen using only $1 of hardware and a little bit of computer vision. The proof-of-concept, dubbed “Project Sistine” after our recreation of the famous painting in the Sistine Chapel, was prototyped by Anish Athalye, Kevin Kwok, Guillermo Webster, and Logan Engstrom in about 16 hours.

See that thing at the top of the laptop? It’s a mirror that’s redirecting the webcam downward to do the detection. How they detect a touch is (at least in principle) simple:

Surfaces viewed from an angle tend to look shiny, and you can tell if a finger is touching the surface by checking if it’s touching its own reflection.