css - How to create an overlay menu from a button in Bootstrap (mobile only) -

i told create separate mobile header our website, looks nothing desktop version. therefore decided create separate file html mobile. don't need responsive across different sizes visible on xs devices. not using bootstrap navbar either added own hamburger menu button visible (on xs devices). here's header.

i want when user clicks menu icon, menu should overlay current page. found slide-in lateral menus didn't because pushed page right. want overlay keep page below is. menu on desktop site looks this:

i'd keep pretty similar, bootstrap styling dropdowns.

what best way go doing this? here's bootply: http://www.bootply.com/mwyq5hvtz0