Dynagraph's graphics window employs a "crystal globe" paradigm in its interaction with the mouse. For effortless manipulation of the displayed objects it helps to be familiar with this paradigm.
One should imagine the displayed object as surrounded by, and solidly attached to, a translucent globe. The centroid of the object coincides with the center of the globe. The globe itself is centered on the window and its diameter equals the window's diameter.
The center of the globe is fixed, but the globe can rotate arbitrarily around it. The mouse pointer grabs and rotates the globe. Since the displayed object is rigidly attached to the globe, it rotates along with the globe.