Making Open.GL mobile-friendly

These commits only affect the layout of Open.GL when visiting from a mobile device (screen up to 1024px).
I made sure nothing is changed when visited from a desktop browser.

I originally was going to put it all in a single pull-request but in order to make it easier for you I decided to split it into two pull-request, and let you choose which one to accept (or none).

Thanks for your awesome work, by the way, Open.GL helped me a lot :)