The Mobilize plugin uses an enhanced version of the mmenu.js jQuery plugin to generate a mobile menu from an existing WordPress menu and displays it for resolutions lower than 720px (width). The menu is assigned via Appearance -> Menus section and can be a new menu or an existing one (usually a duplicate of the main/primary menu).
Mobilize menu accepts an unlimited number of menu levels, using a sliding action to view them. The menu slides in from the left and it is called by the top link ? MENU.
Mobilize works with any theme, provided that jQuery is correctly called in the header/footer.
The backend options are no-nonsense, simple and clear. Declare a menu title (usually “MENU”, or the equivalent internationalized one) and the background color (usually #3a3a3a, which is a dark gray, and it is appropriate for mobile use).