New Card Types — reverse cards, type switching, N-to-N matching, language modes

Currently, when you learn a language, you can only see the flashcards in one direction: either all from your native language to the language you are studying, or the other way around, from the language you are learning to your native language. Instead, it would be better if the cards were mixed, showing some front-to-back and others back-to-front, so that you can naturally train both directions of translation