Duolingo launched an app called Tinycards last year to help you out on subjects other than languages. Unfortunately, it was an iOS exclusive until it came to the web a few months ago. Now, the flashcards app is finally available on Google Play, giving millions of Android-only users around the globe access to its interactive lessons. They will also be able to access the 200,000 custom decks created by veteran users, which include a wide range of topics, including Harry Potter, Game of Thrones and Star Wars trivia. If they can't find anything that suits their purpose, they can always make their own sets, as well.