void OnGUI()
 {
     if (IsSelecting)
     {
         // Create a rect from both mouse positions
         var rect = RTSTool.GetScreenRect(mousePosition1, Input.mousePosition);
         RTSTool.DrawScreenRect(rect, new Color(0.8f, 0.8f, 0.95f, 0.25f));
         RTSTool.DrawScreenRectBorder(rect, 2, new Color(0.8f, 0.8f, 0.95f));
     }
 }
        /// <summary>
        /// Check if it is in boundary
        /// </summary>
        /// <param name="gameObject"></param>
        /// <returns></returns>
        public bool IsWithinSelectionBounds(GameObject gameObject)
        {
            if (!IsSelecting)
            {
                return(false);
            }

            var camera         = Camera.main;
            var viewportBounds =
                RTSTool.GetViewportBounds(camera, mousePosition1, Input.mousePosition);

            return(viewportBounds.Contains(
                       camera.WorldToViewportPoint(gameObject.transform.position)));
        }