a couple things wrong with this script

I am trying to set a target position as mouse position with the on mouse button down then hit a cue ball in that direction with a UI button.

Code (CSharp):

1. public class aim : MonoBehaviour
2. {
3.     [SerializeField] Transform target;
4.     public Rigidbody rb;
5.     public bool strikeBall;
6.     Vector3 targetPos;
7.  
8.  
9.  
10.     void start()
11.     {
12.         targetPos = transform.position;
13.         rb = GetComponent<Rigidbody>();
14.         strikeBall = false;
15.     }
16.  
17.     void FixedUpdate()
18.     {
19.  
20.         if (Input.GetMouseButtonDown(0))
21.         {
22.             targetPos = (Vector3) Camera.main.ScreenToWorldPoint(Input.mousePosition);
23.            
24.         }
25.  
26.         if (strikeBall = !strikeBall) ;
27.         {
28.  
29.             rb.AddForce(targetPos, ForceMode.Impulse);
30.         }
31.     }
32. }

so far the ball likes to target the y axis but x axis seems fixed. I chose my aim script and enable bool from the function list under the UI button but in game the ball targets the button itself on click. I have tried to input.mousePosition.x and y but I got errors. Probably I need to know how to declare input mouse position it up top. if someone tell me how to fix these problems I will appreciate it.