Really good!
A really good, well-designed app. I used this one to learn hiragana and katakana and I highly recommend it. It comes with all the variations: dakuon, handakuon and yōon: the combined characters, and some additional for katakana. There are two ways you can test them: either by speed recognition or stroke recognition. You can choose the speed settings, and I really like the stroke recognition. I used roughly ten minutes a day with this app and it didn't take long time to learn them. I would say this is the best app, but I didn't try any other. I looked at them but they didn't seem as appealing. I think I bought this at a reduced price, but it was worth the money.