anchor.diff:        (bodyA._body.position.y + bodyB._body.position.y) / 2.0
       );
       b2Def.initialize(bodyA._body, bodyB._body, middle);
  +    b2Def.dampingRatio = dampening;
  +    b2Def.frequencyHz = frequency;
       return physicsNode.b2World.createJoint(b2Def);
     }
   }
  
positive.code:   PhysicsJointWeld(
      PhysicsBody bodyA,
      PhysicsBody bodyB, {
        double breakingForce
      }
    ) : super(bodyA, bodyB, breakingForce) {
      _completeCreation();
    }
  
    box2d.Joint _createB2Joint(PhysicsNode physicsNode) {
      box2d.WeldJointDef b2Def = new box2d.WeldJointDef();
  
negative.code:     _completeCreation();
    }
  
    final Point _worldAnchor;
    final double lowerAngle;
    final double upperAngle;
    final bool enableLimit;
  