Best responsive CSS framework so far

There are a lot of CSS frameworks that use a grid system to display content on mobile and desktop(eg.: Bootstrap, Foundation…) but why load a lot of styles that you don’t need on your project? For example a series of form styles when you only need a simple Material Design form?

Lately I discovered Simple Grid, a simple, minimalistic responsive css framework that delivers only the basic functions of the grid.

You can take a look here: http://simplegrid.io/