The app works in portrait mode. There are two clocks for two players. Player 2 starts player's 1clock and the game starts. When one player touch his clock the other's player clock starts. There are multiple time controls you can choose from in the format "minutes | increment seconds". The increment is the time that is added to one's player clock when he finishes his turn and starts the other's player clock. The app can also be used for other games that require a limited time per player's turn.