public void AddUnitPlaceButton(Unit _unit)
    {
        UnitPlaceButton button = Instantiate(Resources.Load <UnitPlaceButton>("Prefabs/UnitPlaceButton"), transform);

        button.SetUnit(_unit);
        AddUnitPlaceButton(button);
    }
 public void AddUnitPlaceButton(UnitPlaceButton _button)
 {
     _button.GetComponent <RectTransform>().position += new Vector3(0, offset, 0);
     offset       += offset_size;
     _button.index = buttons.Count;
     buttons.Add(_button);
 }