A rotational spring, connecting two bodies rotation. This spring explicitly adds angularForce (torque) to the bodies.
The spring can be combined with a RevoluteConstraint to make, for example, a mouse trap.
The relative angle of bodies at which the spring is at rest. If not given, it's set to the current relative angle between the bodies.
Spring constant (see Hookes Law). A number >= 0.
A number >= 0.
Apply the spring force to the connected bodies.