Error Practice Key

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class mouseControl : MonoBehaviour
{

    public float sensitivity = 10f;
    public float maxYAngle = 45f;
    public Vector2 currentRotation;
    Transform player;

    private void Start()
    {
        player = GetComponent<Transform>();

        currentRotation = new Vector2(player.rotation.y*180, player.rotation.x*180);
    }

    void Update()
    {
        currentRotation.x += Input.GetAxis("Mouse X") * sensitivity;

        currentRotation.y -= Input.GetAxis("Mouse Y") * sensitivity;

        currentRotation.x = Mathf.Repeat(currentRotation.x, 360);

        currentRotation.y = Mathf.Clamp(currentRotation.y, -maxYAngle, maxYAngle);

        player.rotation = Quaternion.Euler(currentRotation.y, currentRotation.x, 0);

        if (Input.GetMouseButtonDown(0))
        {
            Cursor.lockState = CursorLockMode.Locked;
        }

    }
}