Responsive typography experiment

Web designer Marko Dugonjic has made an interesting typographic experiment. He created a test web page where the font size is set accordingly to the user's distance from the screen.

The execution of the concept is quite good and implementation could be quite useful, but there are a few problems with this idea. First, the privacy issue of having your webcam staring at you, second, if you move your head while reading it must be quite annoying to see the text moving.