Responsive - Uses styling to add, remove and modify page components, however; all components are loaded, seen or unseen. This focuses on desktop downwards, towards mobile.
Mobile Responsive - Flips responsive upside down, building from the mobile style upwards, adding layers. That means you have only the bare needed basics in the mobile version, adding features and functions as resolution is increased. Unfortunately, this requires variables for use to show or hide template aspects from loading, based on what the real-time browser width is. Hence the need for an add-on to accomplish this.
Whilst I will likely contract this out to Nathan (Naatan), I would love feedback on anything specific users can think of.
Right now, responsive is only half available without variables to enable / disable template aspects / templates entirely.
The Concept Is Simple
A basic add-on that allows the admin to input a handful of screen resolution sizes. For each size, a variable is then available for use in your templates, controlled via normal xen:if statements.
The size you enter is the max-width. Default is normally 480px / 767px that covers both mobile and tablet. Normally 480 and below is complete mobile styling, and 481 > 767 would drop the sidebars. Everything above that should display normally.
Basically, 5 blank options where you can assign a max-width of your choosing, thus obtain that variable for use.
Does it really need anything else?