follow rotation mouse

Unity Engine
1

In my project I have to make an object follow the mouse pointer. With this script it works well the problem is when I turn the object in negative on the X axis that gives problems. How do I solve?

    void Update()
    {
       
            Vector2 mousePos = Camera.main.ScreenToViewportPoint(Input.mousePosition);
            Vector2 posScreen = Camera.main.WorldToViewportPoint(gunPivot.position);
            float angle = Angle(posScreen, mousePos);

            gunPivot.rotation = Quaternion.Euler(new Vector3(0, 0, angle + 180f));
       
       
    }
    float Angle(Vector2 a, Vector2 b)
    {
        return Mathf.Atan2(a.y - b.y, a.x - b.x) * Mathf.Rad2Deg;
    }
2

The simplest way

gunPivot.transform.LookAt(mousePos);

A more elaborate way

// both directions are in world space
Vector3 dir1 = gunPivot.transform.forward;
Vector3 dir2 = (mousePos - gunPivot.transform.position).normalized;
Quaternion q = Quaternion.FromToRotation(dir1, dir2);
gunPivot.transform.localRotation *= q; // local transformation
3

the elaborate way for when XZ are the actual coordinates in 2D

void someMethod() {
  // mousePos is assumed to be Vector2 as well
  Vector2 dir1 = toXZ(gunPivot.transform.forward);
  Vector2 dir2 = (mousePos - toXZ(gunPivot.transform.position)).normalized;
  Quaternion q = Quaternion.FromToRotation(toXYZ(dir1), toXYZ(dir2));
  gunPivot.transform.localRotation *= q;
}

Vector2 toXZ(Vector3 p) => new Vector2(p.x, p.z);
Vector3 toXYZ(Vector2 p) => new Vector3(p.x, 0f, p.y);

there are even more elaborate ways, but if you’re a beginner, I’m sure LookAt will suffice.