To produce motion of a simple object, such as a ball, the object is simply
moved relative to a background display, a little at a time.  This is
simple motion control, and can be accomplished with one animcomp and one
animob, by simply changing the animob's position every n video frames.
The apparent speed of the object is a combination of how often it is moved
(every frame, every other frame, etc.) and how far it is moved (how much
the AnimOb's anx and any are changed).