I’m working on a super basic 2D arcade style game. I have enemies spawning at a random position in the playing space facing toward the player, then moving in a straight line toward the direction they face. I’ve created a variable posDelta to calculate the rotation the enemy should spawn with (in order for them to be looking at the player).
However, when I try to use AddForce() the only way I can get the enemy to travel in the direction they are facing is to use the same posDelta variable as the Vector2 when calling AddForce. This works, but when I multiply that vector by the movement speed variable it causes the speed of the object to be influenced by its random spawn position, as each instantiated enemy will have a unique posDelta.
I’m fairly new to both Unity and scripting, and after hours looking for and trying every solution I can find, I’m stuck. Is there a way to use posDelta as the direction of force while modifying speed in a different place? Am I just missing something obvious?
Thanks in advance 
public Rigidbody2D enemyRb;
public float moveSpeed = 5;
private GameObject player;
private Vector3 posDelta;
private Quaternion lookRotation;
void Awake()
{
enemyRb = GetComponent<Rigidbody2D>();
player = GameObject.Find("Player");
}
// Start is called before the first frame update
void Start()
{
//Find delta between player and enemy
posDelta = (player.transform.position - transform.position);
SetRotation();
}
// Update is called once per frame
void Update()
{
}
void FixedUpdate()
{
MoveEnemy();
}
private void OnTriggerEnter2D(Collider2D other)
{
if(other.tag == "Player")
{
Debug.Log("Player Hit");
}
}
void MoveEnemy()
{
//Add Force in the direction of movement * movemenet speed
enemyRb.AddForce(posDelta * moveSpeed * Time.deltaTime, ForceMode2D.Impulse);
}
void SetRotation()
{
//Find relative position
var relativePos = player.transform.position - transform.position;
//Calculate rotation needed to face target
var zAngle = Mathf.Atan2(relativePos.y, relativePos.x) * Mathf.Rad2Deg;
//Rotate enemy by zAngle
enemyRb.transform.Rotate(0, 0, zAngle);
}