one row will divide to the number of parts, if you just set class='c'

on large screens if you just set class='x', it will take the x class ratio

three equal parts

sum of parts is 12, every part will take ratio of it's class number

it will take just 6 part of 12

float right boxes, by .os class

Responsive on medium devices, like tablet's by .m classes

Responsive on mobile devices by .s classes