Responsive design typically focuses on screen sizes, but that's just the practical application of the larger goal – making a website function well no matter how or where you are viewing it. The emphasis ultimately is on you, not your device.
Developer Marko Dugonjić takes responsive design's emphasis on you to new levels of interactivity with his experiment in typesetting by face detection.
Using a very cool JavaScript headtracking library – which taps WebRTC and getUserMedia to access your webcam – Dugonjić's app calculates how close you are to the screen and adjusts the font size to make text more readable.
To see it in action, head on over to the demo page and grant it permission to use your webcam. For the most useful example, check out the onload-based implementation, but for a better sense of how it works be sure to try the "Realtime" version.
It may not be the most practical experiment and how well it works depends on plenty of factors well beyond the control of the site (how good your eyes are, whether or not you're wearing your glasses and so on), but it's not hard to imagine how this could be very useful in some situations – for example, bumping up font-size when your site is displayed on a television.
When you're done playing with the resizing demo be sure to check out Dugonjić's more practical and more immediately useful Typetester.
