anchor.diff:      this.friction = friction;
       this.restitution = restitution;
       this.isSensor = isSensor;
  +
  +    this.linearVelocity = linearVelocity;
  +    this.angularVelocity = angularVelocity;
  +    this.angularDampening = angularDampening;
     }
   
     Object tag;
   
  -  PhysicsShape shape;
  +  final PhysicsShape shape;
   
     PhysicsBodyType type;
   
  
positive.code: 
      if (_body == null)
        return;
      for(box2d.Fixture f = _body.getFixtureList(); f != null; f = f.getNext()) {
        f.setSensor(isSensor);
      }
    }
  
    Offset linearVelocity;
    double angularVelocity;
  
    double linearDampening;
  
    double angularDampening;
  
    bool allowSleep;
  
  
negative.code:     double friction: 0.0,
      double restitution: 0.0,
      bool isSensor: false,
      Offset linearVelocity: Offset.zero,
      double angularVelocity: 0.0,
      this.linearDampening: 0.0,
      double awakeangularDampening: 0.0,
      this.allowSleep: true,
      this.awake: true,
      this.fixedRotation: false,
  