An articulated arm using yesterday's constraint-based simulation code.

There's just one new kind of constraint added here - one to keep the "shoulder" of the arm fixed. Of course, as described in Jakobsen's article, further constraints would make the motion of the arm more realistic.

Of note is the way the arm behaves when the hand is moved far away from the shoulder. It stretches out in an attempt to meet the competing mouse and fixed-shoulder constraints. This could possibly be used to develop a sort of cartoony "stretch" for long reaches in a game or animation.