need help regarding rotating arm

hello guys/girls

i am trying to implement 360 aim with a 3d model in 2d world (Unity Engine) so far its working only when character is facing right when i rotate my character to face it left (-90 degree) . character's arm looking at mouse position until character face left i tried flipping angles direction multiplying by 1 and -1 but its working in reverse instead. here's code i am using for arm rotation.

 [SerializeField] Transform armToRotate;
 
  // arm rotation fixer
 
   [SerializeField] float mod;
 
 
 
 void Update()
 
 {
 
  lookAtPos = Camera.main.ScreenToWorldPoint(CrossPlatformInputManager.mousePosition);
 
 
 
     LookAtMouse();
 
 }
 
 
 
  void LookAtMouse()
 
   {
 
     if (bodyToRotate.rotation.eulerAngles.y == 90f)
 
     {
 
       mod = 1;
 
       print("90");
 
     }
 
 
 
     if (bodyToRotate.rotation.eulerAngles.y != 90f)
 
     {
 
       print("-90zzz");
 
       mod = -1;
 
 
 
 
 
       armToRotate.localEulerAngles = Vector3.zero; // added just maye previous rotaion is bugging new rotations (honestly no idea)
 
 
 
     }
 
 
 
 
 
     armToRotate.localEulerAngles = Vector3.zero; // added just maye previous rotaion is bugging new rotations (honestly no idea)
 
 
 
     Vector2 lookDir = lookAtPos - armToRotate.position;
 
     float angle = Mathf.Atan2(lookDir.y, lookDir.x) * Mathf.Rad2Deg * mod;
 
     armToRotate.localEulerAngles = new Vector3(angle, 0f, 0f);
 
   }