If you are progressing through a lesson answering questions and you (stupidly) as I did press the back button thinking it would let me go back to the previous question, instead you are thrown out of the lesson and back to the previous page you were in.
I don’t think it’s really necessary to add a way to back up, but I do think that when a lesson is in progress and the user presses back, it would be nice to get confirmation from them that they will be abandoning the lesson. I think you might be able to do this with a beforeunload
event handler, but I’m not sure how tightly bound the web site and app are and whether this would make things worse on the site.