We recommend that our users take classes on their computer or possibly template rather than mobile device.
The most obvious reason is that by entering the class on your computer, your screen size gives you much more room to use the online whiteboard.
Secondly, this encourages you or your students to take the class in a quiet, stable place. It's obviously much harder to learn on a noisy bus than a quiet room. In group classes, this is especially important where it's unfair on other students if the background noise is too much.