50,000 downloads from the Apple Store.
This app is for beginners of Japanese to learn Hiragana, Katakana and almost 1000 words of really useful basic vocabulary.
Get a card right and it will be taken out of the drill. Get it wrong and it will be shuffled back in until you do get it right.
The key to learning kana and building vocabulary is regular review.
Every moment that you have a chance, take out your phone and do a practise drill.
Practise every day and watch your vocabulary grow.