Bunpro takes a similar approach to the WaniKani system of spaced repetition with typed answers. But instead of kanji, it teaches and reinforces grammar. Linking to free grammar resources outside the app like Tae Kim and PuniPuni, Bunpro splits grammar up by Japanese Language Proficiency Test (JLPT) levels. Those levels (N5–N1) are then split into ten groups.
Clicking on a grammar item shows meaning, grammatical structure, simple example sentences, and two or more outside explanations to help you learn the grammar point. This is where you'll be able to click directly to a free resource, read through, and then come back and click the little checkbox to tell Bunpro you learned it. Once all the supplied grammar points have been learned, they'll enter your review queue.
Bunpro gets huge bonus points for forcing users to type, actually making them recall the answer.
Reviews show you the sentence examples from the lessons (one at a time) with a text field to submit your answer. Bunpro gets huge bonus points for forcing users to type, actually making them recall the answer. Multiple choice is the favorite of language learning apps, but it just tricks your brain into thinking you really know it.
Other great things about Bunpro: the English translation/hint can be toggled (we recommend keeping it off if you can), and the IME automatically converts to Japanese for you.
The little arrow under the text field lets you review entire lessons, if you get an answer wrong or if you just need a refresher. Reviews are SRS-based, meaning the more you get them correct, the longer the intervals between those reviews. The more you get wrong, the shorter the intervals between those reviews.
You can also look at your user page to see your progress, number of correct answers, and when your reviews will be coming back around.
The site currently has grammar for JLPT N5–N3 as of the end of September, with active bug fixes and improvements being done by the creators. This little site has a ton of potential, so we'll be keeping our eyes on it.