How do you "master" a topic?
I get these email reminders suggesting I "master" a topic that I've already "learned". The emails take me to the topic, but it's no longer clear what I'm supposed to do next. There used to be lots of lessons laid out to master something, but they are gone.
Also, it seems that I am never asked to translate anymore. That used to be part of mastery. Now, I guess, that's totally optional. (Given that translation of material is one of DuoLingo's goals, is that a good idea?)
There are no separate "learning" and "mastering" now. You do all the lessons in the unit, then return to it from time to time to review.
The idea is that with learning a language you can hardly "master" anything once and for all. Translating a few sentences usually has nothing to do with mastering new words from the unit. With the old system it was not obligatory, too, you could test out of the skill and get the "mastered" badge.