It's called "KSEG". Ask your synaptic package manager to look for it, and while at it also install "KIG", a similar toy. After opening KSEG, look at "help" and read. After 10 minutes you ought to be able to reproduce a moving picture of the theorem of Pappus, [Theorem of Pappus|http://en.wikipedia.org/wiki/Pappus's_hexagon_theorem].
