This app is really well done. Polished and fun, and Im learning kanji very rapidly by playing it for a few minutes a day — which is easy to do, since theres a simple but fun story that makes you want to keep playing.
My only regret is that the app teaches you only the meanings of the kanji, not the readings. I hope the authors put out more apps in the future, and include the primary reading for each character.
JoeStrout about Ninja Words Adventure