We recommend using the biggest one you have, such as a laptop or desktop computer, as this will give you the best learning experience on the course.
The course is mobile and tablet friendly but do remember mobile data internet is not as stable as wi-fi or cabled internet so there is a chance the signal could drop out and some of your progress lost. If you are having any problems on a particular device we'd recommend trying another one to see if this fixes any problems you are having.