Say there is a rectangle of 100 x 100 units on the x-y plane with the rectangle's center at the origin.

I want the rectangle to rotate slowly by 20 degrees anti-clockwise from the point of rotation (on the cartesian plans) as (20,20). After rotating the 20 degrees, it rotates clock-wise 20 degrees from the same point of rotation back to its original position.

It then immediately rotates clockwise from the point of rotation (on the cartesian plans) as (-20,20). After rotating the 20 degrees, it rotates anticlock-wise 20 degrees from the same point of rotation back to its original position.