Even worse, it is (or at least was) not available in all methods used to access the content. I think it is available on the web, where I started using Duolingo

Even worse, it is (or at least was) not available in all methods used to access the content. I think it is available on the web, where I started using Duolingo during a downtime at work, and when I later wanted to continue, I just did not find the button for it on the iOS app (or the other way around). That is pretty terrible for such a basic part of the learning experience.