> Then there's also a "barbell" which you can press and takes you into some lesson, but I never quite figured out what it did.
It takes you into a lesson that it thinks you should review next. Duolingo is meant to implement spaced repetition in that it keeps track of all the times you have seen every word, and it tries to give you lessons that are "due" for repetition according to its algorithm. In the web interface they show you how "strong" each word is in their opinion, but I found that their data on when you last saw a word was buggy.
Anyway, the barbell is useful to keep you up to speed by revisiting stuff once you have finished all the lessons once.
It takes you into a lesson that it thinks you should review next. Duolingo is meant to implement spaced repetition in that it keeps track of all the times you have seen every word, and it tries to give you lessons that are "due" for repetition according to its algorithm. In the web interface they show you how "strong" each word is in their opinion, but I found that their data on when you last saw a word was buggy.
Anyway, the barbell is useful to keep you up to speed by revisiting stuff once you have finished all the lessons once.