Stopped: just dots on a flat screen, with no ball in them.
Tricks of motion
Kinetic depth effect
What do the dots make?
A ball spinning in 3D, though the dots only slide left and right. Keep watching and it may suddenly spin the other way.
Why? Your brain knows that the near side of a turning ball moves one way and the far side the other, so moving dots are enough to build a ball. With no clue to which side is near, it can flip, like the spinning dancer.
Picture: Drawn by Science Playground · Wikipedia(opens in a new tab)