This tests your reaction time, or how fast you react to a change. The instructions are in the game. The average human reaction time is 250ms (milliseconds), but it's normal to get over 300 on this test especially if you are young and/or your device is slow (it may slow down your score up to 50-100ms) my reaction time is 429 milliseconds to be honest, but I'm pretty young. And after a few attempts, it's 331.
