12sep11 OK ... a lot of Stan's translations of Hippocket programs has a design change that seems to be non-trivial to back-engineer. For example Lou Kauffman's Juliaset program. In the dynamical systems the dynamical sytems is drawn directly into the viewable screen (no double buffering, therefore no need to store the trajectories. Therefore you can watch the evolution and get a motivation for the trails in the dynamical systems simulated in swapbuffers OpenGL. But Stan somehow manages to show only the "end result". I don't know if this is a pedagogical policy, a step in a construction in the text, or what. An any event, we want to restore the original concept.