Hello, again,
Well, actually the plugin is device-agnostic. It only takes into account such device properties as its dimensions and its pixel ration and combines them with its user-defined settings at each particular time, in order to determine the most appropriate and fitting image size to serve.
So if, for instance, the breakpoints that you set in your Adaptive Images settings page are big enough then they should cover desktop devices as well. However, usually there is a lot more to gain when focusing on mobile devices. But the settings are there to experiment as much as you like.
Lastly, this whole algorithm lies in the adaptive-images-script.php of the plugin code, but it is quite a lot more that one piece of code.
Cheers,
Takis