This project shows the differences between the original foundation based on SASS, and one that I have converted into Stylus here
grunt
This builds the scss version of app.css into dist/scss/app.css, and stylus version of app.css into dist/stylus/app.css. It also starts a local server so you can open http://localhost:3000 to see the stylus version and open http://localhost:3000/scss.html to se the scss version.
Filed css.diff contains the output generated by running git diff HEAD:dist/scss/app.css HEAD:dist/stylus/app.css > css.diff