This is the code for my Responsive Typography workshop first given at ATypI Warsaw in September 2016.
Now with variable font demo!
Based on work done by @litherum in WebKit, you can now download the WebKit Nightly build (on a Mac) from https://webkit.org/downloads/ and try out variable fonts!
Check out 'html/varfonts.html' and 'css/varfonts.css' to see how it all comes together. This is using Skia (installed with MacOS), so it's not a true variable font (and the spacing is not the best), but the CSS syntax is there and it responds nicely to Media Queries.