private void BuNext_Tapped(object sender, EventArgs e)
        {
            if (TutorialIndex <= Tutorials.Count - 1 && IsLast == false)
            {
                TutorialIndex++;
                ActiveTutorial = Tutorials[TutorialIndex];

                if (CheckLast())
                {
                    IsLast = true;
                }
            }
            else
            {
                FinishAction.Invoke();
            }
        }
 /// <summary> Finish shader. FinishAction is called </summary>
 public virtual void Finish()
 {
     FinishAction?.Invoke(this);                           // any shader hooks get a chance.
 }