if(Input.GetMouseButtonDown(0)) //if mouse 1 pressed, begin selection box
        {
            selecting = true;
            mousePosition1 = Input.mousePosition;
        }
        if(Input.GetMouseButtonUp(0))
        {
            selecting = false;

            // Dragging selection.
            if(Vector2.Distance(Input.mousePosition, mousePosition1) > 2f)
                CheckForUnits ();
            else
                ClickSelection ();
        }