Bunkado

Bunkado 文カード means Japanese sentence cards. It is a spaced-repetition flashcard app to learn grammar structures and sentence patterns, while picking up new vocabulary along the way.

Simply swipe left on cards that you can't read/understand, and swipe right on those that you can. The algorithm, over time, will feed you those cards that you need more practice with. And don't forget to press the eye button to reveal the translation when you are stuck.