Kakugo

Kakugo makes learning Japanese fun and efficient with quizzes on hiragana, katakana, kanji, and vocabulary. Its smart spaced repetition adjusts to your pace, whether you're studying 30 or 100 kanji a day. It's sorted by JLPT levels, has unlimited quizzes, no ads, works offline, and is open-source. Great for commutes or focused study—start anytime!