Ошибка в Unity

Код:
using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class Enemy : MonoBehaviour
{

public float speed;
public float StopDistance;

private float TimeBtwShots;
public float StartTimeBtwShots;

public GameObject projectile;

private Transform player;




void Start()
{

TimeBtwShots = StartTimeBtwShots;
}


void Update()
{
if (TimeBtwShots <= 0)
{
Instantiate(projectile, transform.position, Quaternion.identity);
TimeBtwShots = StartTimeBtwShots;

}

else
{
TimeBtwShots -= Time.deltaTime;
}

}
}