A free program for Android, by Bhima Apps.

Unlock the Lock is an extremely simple, addictive, & fun game to play on your smartphone or tablet. If you are looking for a game to play on your Android device that is easy to play, but at the same time, provides you with a challenge, then this game is definitely for you.

A little horizontal line starts to rotate counterclockwise. Just as the line touches the blue dot, you must tap the screen. When that happens, the line starts to move, and you have to tap it on a different dot. The line then resumes rotating in a clockwise direction, and so on.