I'm sure that, once upon a time, there was the ability to restrict the visibility of an activity or resource based on whether the user was viewing it on a mobile device or a desktop browser. This way, one could create content that looked good in both situations. 

I can no longer find this feature, so I'm wondering if my memory is just off or maybe was something that existed before the days of responsive web design in Moodle.

Can someone confirm or deny the existence of this feature?