This is a lovely app.
Since I started using this app for my English Study, I've made and shared many manuals for Korean users through Internet.
Our cafe is continuing to grow and has now about more than 4,000 users at home.
With so many other flashcard apps with some worst performances and algorithm,
the only reason that FD is still ranked rather lower on the list of the Korean appstore is just it's not yet been localized.
So, why don't you try to translate your app into some other languages for uses abroad?
If you need any help with translating the menu stuff into Korean, I'd be glad to help.
cafe.naver.com/flashcardsdeluxe