circle of violet dots

You see a circle of violet dots. Each of them disappears in order, like moving in a circle.

Concentrate your sight at the cross, and then you can see how the violet dots disappear.

If you do it right, you can see that the green dot is moving.

If you keep looking, all the violet dots will disappear and only green dot will keep moving!

From: JeanAustria@astec-power.com