Far simpler than editing theme files

Great plugin, essential, elegantly simple. The css is stable, unlike css in a theme that could be over written with a theme update.
I have given this 5 stars as its so good in its basic form, but I seriously considered a 4 star rate because there is a lack of documentation as to the criteria by which the mobile css file is invoked by mobile devices, and therefore which devices use it. The workround is @media filters in the main stylesheet. Lets have some clarification please.