anchor.diff:        return position;
       } else if (physicsParent is PhysicsGroup) {
         // Transform the position
  -      Matrix4 inverseTransform = new Matrix4.copy(physicsParent.transformMatrix);
  -      inverseTransform.invert();
  -      Vector4 parentPos = inverseTransform.transform(new Vector4(position.x, position.y, 0.0, 1.0));
  +      Vector4 parentPos = physicsParent._inverseMatrix().transform(new Vector4(position.x, position.y, 0.0, 1.0));
         Point newPos = new Point(parentPos.x, parentPos.y);
         return _positionToPhysics(newPos, physicsParent.parent);
       } else {
  
positive.code:     _transformMatrixBoxToNode.invert();
  
      return _transformMatrixBoxToNode;
    }
  
    /// Converts a point from the coordinate system of the [SpriteBox] to the local coordinate system of the node.
  
negative.code:   /// changes that affects the matrix.
    void invalidateTransformMatrix() {
      _transformMatrix = null;
      _transformMatrixInverse = null;
      _invalidateToBoxTransformMatrix();
    }
  
  