Click the color of object shown at the bottom of the screen as it flies by. Ignore the shape - It's just there to trick you :) You one score for missing, and lose one for a correct hit. After two minutes, the game will stop and your score will show. Lower scores are better. Moderate mode has three colors, Hard has five, and Nope has seven. Watch out for gold.
Another one of those tiny games I'm so fond of. Don't worry, I'm still very much inactive. As usual, I got lazy on the home stretch - the audio and score display are meh. *Shrug*