class Engine
    {
        public static RenderWindow app;

        public static void Main (string[] args)
        {
            app = new RenderWindow (new VideoMode (64*8, 64*8), "Test",Styles.Resize);
            app.Closed += (sender, e) => (sender as RenderWindow).Close ();

            Texture t = new Texture ("texture.png");
            Sprite background = new Sprite(t){ Scale = new Vector2f(8,8)};

            while (app.IsOpen()) {
                Update (app);
            }
        }

        public static void Update(RenderWindow window)
        {
            //Что лучше юзать переменную window или app?
        }
    }