private void PopFade(IStateMachine stateMachine)
        {
            stateMachine.FinalizeTopHandler();

            Engine.Instance.FadeTransition(() =>
            {
                stateMachine.RemoveTopHandler();
                stateMachine.ResumeDrawingTopOfStack();
            },
            () =>
            {
                stateMachine.ResumeTopOfStack();
            });
        }
        private void PopFade(IStateMachine stateMachine)
        {
            stateMachine.FinalizeTopHandler();

            Engine.Instance.FadeTransition(() =>
            {
                stateMachine.RemoveTopHandler();
                stateMachine.ResumeDrawingTopOfStack();
            },
                                           () =>
            {
                stateMachine.ResumeTopOfStack();
            });
        }