I am using some basic grid functionality from Bootstrap v3, but the names are changed to col-* (number), because the mobile version always stacks with the 12 column grid. Have new mixins for the size, I am using @screen-tiny, @screen-phone, @screen-medium and @screen-large, because it is easier to identify.
The project is using less files, and the style.less is compiling it to a css, that way I can seperate all my sections in the code.