Pretty good

This app is much like the classic Piano tiles. Outside multiplayer, the gameplay is the same, except you can use your own music instead of the classical if you like.

The multiplayer function is addicting. I found the app two days ago, and Ive already played more than 200 games. I have some prior experience from classic piano tiles, so I was able to jump right in. In order to play, you bet either energy (Z) or real money. The energy replenishes through a gift system, and you should never really run out as long as you arent too bad. Money is another story. You are given a small amount of it through achievements, but after that it is impossible to replenish without "making a deposit". This means giving the app access to your credit card/PayPal. I would not recommend this, as the app is kinda buggy, and lag can cause you to lose games and thus money. As long as you dont put any money in, everything that comes out is profit!

Death by dragon fire about Piano Tiles - 4 : Real Cash Multiplayer Tournaments