Kakugo

Features include:

• Hiragana, Katakana quizzes • Kanji quizzes by reading and meaning • Kanji test by part composition • Kanji writing test • Vocabulary quizzes by reading and meaning • Unique spaced repetition formula that adapts to your own learning pace • Unlimited quiz sessions that allow you to take a quiz at any time, for however long you want, useful to efficiently spend commuting time • Show similar-looking kanji in answers to teach you the differences • Kanji and vocabulary sorted by JLPT • Clicking on kanji opens aedict3 (a non-free Japanese dictionary) or jisho.org • Optimized tablet support • Open source • No ads • No internet access required • More to come

What makes it different from other apps:

• a custom SRS formula that adapts to each person's level and learning pace • unlimited quiz sessions that can be stopped at any time • "don't know", "maybe" and "sure" buttons that helps Kakugo determine how well you know a character • a harsher penalty when the answer is wrong to help you learn the character well • kanji similar to the one in the question are shown as answers to help you learn the subtle differences between them • it's free and without ads