Rotation
Snail Rotation
Snail Rotation
Even if I didn't have a coordinate plane, I would know that this is a correct rotation because the snail keeps the same distance from the center of rotation on all images. The center of rotation is the fixed point, which all the objects move around. Also, I could measure the angle of rotation for each image and see if it matches up with each of the other images angles of rotation. I would also check to make sure that the rotation didn't map back onto itself, unless I knew that it was a 360° rotation.