In order to achieve the highest possible score in 4 difficulty levels, you have to tap the color shown above within a certain time. When the time is up, or if you touch the wrong color, the round is over.
With the GameCenter you can see and challenge the highscores of your friends and all other players.
In addition, if you play the game on multiple devices, all highscores and the current level of difficulty will be synced between iPhone, iPad and Apple Watch.