protected virtual void GetTower()
{
//transfer the mouse position to the world position
Vector3 screenPoint = Camera.main.WorldToScreenPoint(transform.position);
Vector3 startDragPos = Camera.main.ScreenToWorldPoint(new Vector3(Input.mousePosition.x, Input.mousePosition.y, screenPoint.z));
//spawn the selected tower
GameObject tower = Instantiate(towers[selectedTower], startDragPos, transform.rotation) as GameObject;
//set the right start properties of the tower, so it knows its being dragged.
mouse.SetTarget = tower;
Drag drag = tower.GetComponent <Drag>();
drag.StartDrag();
drag.SetKinematic = false;
}