Source for graphics demos?

[A JETSON News User]

Does anyone know where I might find the source for a fairly common
graphics demo that I don't have the name for.  It is the one that
is a stick that flies around the screen randomly and draws a 
pattern like a spirograph in the process.  Some systems use it so
that the screen doesn't get etched.  What I eventually want to do
with it is port it to an IBM PC.  Direction to it and other C source
            code for cool graphics demos would be most appreciated. 

Thanks,

Ignacio Valdes