Piano Tiles (iOS) or Don't Tap the White Tile (Android) is an incredibly addictive game with two different names. The concept is easy, but the game is incredibly hard to put down once you start playing.
There are five different game modes, but the core principles are the same: touch the dark tiles as they scroll down the screen, and don't make any mistakes.
The classic mode requires you hit 50 tiles in the least amount of time possible. When you reach the green finish line, you'll get to see how fast you completed it.
At the end of every game, you'll get to see how you did against your previous high score.
Editors' note: I can't claim the high score pictured in this slide -- it was done by CNET's Lynn La who is a Piano Tiles expert.
The object of the game is to only touch the black tiles. When you slip up, the game makes sure to let you know.