Enemy Detection

Hi everyone, I'm very new to making games and coding so i started watching some tutorials online. I'm pretty deep in making my game and now I'm working on the enemies (flying), but the way my script has it is the enemy just takes your position(wherever you may be) and moves to it(explodes on contact with you). And there's nothing wrong with that except that this is a side scrolling game and i don't want the enemies to move to me until i am a certain distance from them. Is there a way i can do this?
I have 3 enemy scripts what should i change to get the effect that i need?

 

you can check the distance between player and enemy and then move the player if the distance is lower as you want.
The distance can be calculated from vector from enemy to player. This vector is vector subtraction: end point - start point. Magnitude of this vector is the distance. I think, EnemyAI is your moving script. In C# you will need float variable for distance when enemy should move (you can change it later in inspector). Place the line in EnemyAi somewhere at 28 line.

Code (CSharp):

1. public float distanceToPlayer = 5;

Then check the distance, befor moving your player and move, if magnitude of vector between enemy and player is smaller then your "distanceToPlayer". Replace 109 line.

Code (CSharp):

1. if (Vector3.Magnitude (target.transform.position - transform.position) < distanceToPlayer) {
2.             rb.AddForce(dir, fMode);
3.         }

I am not sure, that it will work at first run, maybe something is wrong

and check Unity manual (you should use sqrMagnitude to avoid extra cpu calculating):
https://docs.unity3d.com/Manual/DirectionDistanceFromOneObjectToAnother.html