Turret.cs

public class Turret : MonoBehaviour {
    private Camera _cam;
    [SerializeField,Range(1,100)] private float _rotationSpeed = 1;
    [SerializeField] private Projectile _projectilePrefab;
    [SerializeField] private Transform _spawnPoint;

    void Awake()
    {
        _cam = Camera.main;
    }

    // Update is called once per frame
    void Update() {
        var mousePosition = _cam.ScreenToWorldPoint(Input.mousePosition);
        mousePosition.z = 0;

        transform.up = Vector3.MoveTowards(transform.up, mousePosition, _rotationSpeed * Time.deltaTime);

        if (Input.GetMouseButtonDown(0)) {
            Instantiate(_projectilePrefab, _spawnPoint.position, Quaternion.identity).Init(transform.up);
        }
    }
}