Y forward on rotation not X

I found this script on the forums which works for what I need but it sets up the X to look at the object while I need -Y to look at the object.

Anyone know what set up I could use to change this??

 private var mousePos : Vector2;
    
    
 private var screenPos : Vector3;
  
     function Update () {
     mousePos = Input.mousePosition;
     screenPos = Camera.main.ScreenToWorldPoint(Vector3(mousePos.x, mousePos.y, transform.position.z - Camera.main.transform.position.z));
  
     transform.rotation.eulerAngles.z = Mathf.Atan2((screenPos.y - transform.position.y), (screenPos.x - transform.position.x))*Mathf.Rad2Deg;
     }