A free program for Android, by Jernung.

Play entertaining and engaging games in space to learn Japanese! No multiple-choice questions, flashcards, or other dull exercises. The Infinite Japanese app will surely help you improve your knowledge of Japanese words and sentences.

This will also help you recognize more than 200 words. To encourage greater memory recall, questions are posed in three different orders and incorporate text, audio, and icons. You can also play a hard review game to go over all the words in each category. To suit your preferred learning style, alternate between romaji, kana (hiragana & katakana), and kanji. Download the app now and try it for yourself!