In process of adding Creative Blog's responsive css-only dropdown menus to my basic adaptation of Eddie Machado's Bones theme, as a starting point for my own theme development. (http://www.creativebloq.com/css3/build-smart-mobile-navigation-without-hacks-6122800)

Switched nav to content-first, i.e. moved the nav to after the main content and sidebars.

Basic styling of dropdown working, but need to style the menus nicely (!) and get the "back to content" link working properly.
Still developing basic bones with content first css-based nav.

First level nav now working correctly, but still need to sort out how best to construct accordian nav for second level.