/// <summary>
        /// draws a GL quad, textured with an animation.
        /// </summary>
        /// <param name="rectangle">coordinates ofthe GL quad</param>
        /// <param name="totalSeconds">animation position in seconds</param>
        public void Draw(IReadOnlyBox2D rectangle, float totalSeconds)
        {
            var id        = CalcAnimationSpriteID(FromID, ToID, AnimationLength, totalSeconds);
            var texCoords = SpriteSheet.CalcSpriteTexCoords(id);

            SpriteSheet.Activate();
            rectangle.DrawTexturedRect(texCoords);
            SpriteSheet.Deactivate();
        }