It is a very underrated mode and it needs improvement. People learn very well familiarizing with the language, it is something that you can't achive only doing flashcards.
  1. It needs more than one example sentence, i had this mode on for around 20 minutes and i heard the same sentences on and on.
  2. Option "use unfamiliar words" should be added. Either train the AI to use words that are simmilar level to mine or add an option to choose difficulty manually.