Making the camera rotation in line with the ball

Hi,

I have 3d ball player object that travels inside a 3d pipe. It is followed by a camera. At the moment, as the ball goes from side to side, the camera rotation does not change. What I am trying to achieve is that camera rotates along the single axis in line with the ball's position on the wall of the pipe.

Current set up:

What I am trying to achieve is this:

My current code is as follows:

 public class CameraFollow : MonoBehaviour
 {
     public GameObject ball;
     // Start is called before the first frame update
     private Vector3 _offset;

     void Awake()
     {
         _offset = new Vector3(10,5, 0);
     }
 
     // Update is called once per frame
     void FixedUpdate()
     {
 
         transform.position = ball.transform.position + _offset;
         transform.LookAt(ball.transform);
     }
 }

I tried using euler angles but it did not work as intended. I am sure the solution is fairly straightforward but I just don't get it. Any help would be appreciated.