There's a blue ball, that follows the Mouse. You need to touch the green balls to gain points. When you touch a green ball, a red ball is added. If you touch the red balls, you lose points. After two minutes of play, the game will see the actual score and it will be submitted.
The blue ring will follow the Mouse. Touch the green rings and avoid the red ones.
A context menu should be shown when right-clicking or, on touch devices, long-pressing in the game. This menu especially allows to play in full screen and control the volume.