purecss blog theme comments grid

Short Version: 1. Make 3 sections using grids in purecss, currently there are 2, the menu and the article, add a 3rd for comments on the right side. 2. Make the site collapse to mobile view under 1500px. Long Version: I am using the purecss [login to view URL] from [login to view URL] As you can see there is a nav bar on the left side. I would like to replicate that and put a section on the right side for blog commenting. The layout is responsive so when viewed on a phone the left nav goes to the top and the article below, I would like the comments to also go below the article on phones. Please work on the Codepen here [login to view URL] I made the gird based on 5ths, 1/5 for the menu, 3/5 for the article and 1/5 for the comments. pure-u-md-1-5 / pure-u-md-3-5 / pure-u-md-1-5 I have made a mockup in photoshop showing want I hope to achieve. Mockup here [login to view URL] Furthermore, currently the html using pure-u-md-1-5 \"md\" according to [login to view URL] will switch to the mobile view when the browser is less than 768px. I would like to the site to switch to mobile view on anything 1500px or less. (nav on top, article in middle, comments on bottom)