Reachmahjong.com

The game is a practice game about waits, you can select to have to guess the wait of a 7, 20, or 13 tiles hands and can set the amount of time given to do the task. 30 or 60 seconds.

I didn´t try it. So i don´t know how good it is.

The name is まちあて.https://play.google.com/store/apps/deta ... hjong.quiz

Ok, I tried it a bit. It's that kind of wait trainers with just one suit, characters in this case. Cool to train your head with multisided waits, and a good way to get used to the characters suit.