anchor.diff:      this.worldAnchor, {
         this.lowerAngle: 0.0,
         this.upperAngle: 0.0,
  -      this.enableLimit: false
  -    }) : super(bodyA, bodyB) {
  +      this.enableLimit: false,
  +      double breakingForce
  +    }) : super(bodyA, bodyB, breakingForce) {
       _completeCreation();
     }
   
  
positive.code: part of skysprites;
  
  abstract class PhysicsJoint {
    PhysicsJoint(this.bodyA, this.bodyB) {
      bodyA._joints.add(this);
      bodyB._joints.add(this);
    }
  
negative.code:     this.groundAnchorB,
      this.anchorA,
      this.anchorB,
      this.ratio, {
        double breakingForce
      }
    ) : super(bodyA, bodyB, breakingForce) {
      _completeCreation();
    }
  
  