The green ball will start in the middle. Move your mouse and try to avoid getting touched by the green ball. If you get touched (the ball will turn purple) you will have to shake it off. Move your mouse back and forth repeatedly (actually just move the pointer quickly 4 times with no pauses in the middle; the ball will gradually change color) in order to shake it off. It will then start chasing you again.
Score mode doesn't work quite yet, so...
