Impressive accomplishment in what I assume is a tiny code size. I love the fading trail. A couple of things don't seem quite right to me but I really don't know what. Some guesses: a) Perhaps there is a decay/friction fudge factor that you have set so it actually adds a little energy on each iteration? Makes it a little more exciting to begin with, but then it just goes berzerk. b) This one is more subtle and may be my intuition playing tricks on me. Sometimes it looks to me as if the joint between the two arms is "too stiff" - little or no change when my intuition tells me it should be changing more. (But other times I don't see that; in fact sometimes the outer pendulum spins more crazily than I'd expect. Dunno.)

Anyway, impressive.