How to set menu items on mobile as stacked full-width items? I am using Superfish, and my menu is perfect for normal displays.  However, for small smartphone displays, I want my menu items stacked and spanned the width of the display.  Also, when an item is clicked with child items, the top level items go away and display the child items.

I can't figure out how to do this from the SF documentation or searching on the web.
I've only used Responsive menus on one project and it seemed to work fine, outputting the mobile menus when viewed by a device, and the normal menu when viewed by computer with some margin of error but in general it seemed to work well. You can see a demo here: http://drastikbydesign.com/demo/responsive-menus-demo-1-mean-menu and how it shows on a mobile and/or computer.