Basic Unity 3D Enemy follow Script

This script essentially allows the player to be followed by another "enemy" object. It's a .js you need to attach to your GameObject to instantiate.

1. var closeEnoughDistance = 1; // stop moving once we get this close to the target
2. var target : Transform; //the enemy's target
3. var moveSpeed = 3; //move speed
4. var rotationSpeed = 3; //speed of turning
5. var attackThreshold = 1.5; // distance within which to attack
6. var chaseThreshold = 10; // distance within which to start chasing
7. var giveUpThreshold = 20; // distance beyond which AI gives up
8. var attackRepeatTime = 1; // delay between attacks when within range
9.  
10. private var chasing = false;
11. private var attackTime = Time.time;
12.  
13. var myTransform : Transform; //current transform data of this enemy
14.  
15. function Awake()
16. {
17.     myTransform = transform; //cache transform data for easy access/preformance 
18.     }
19.  
20.  
21. function Start()
22. {
23.      target = GameObject.FindWithTag("Player").transform; //target the player
24.     }
25.  
26. function Update () 
27. {
28.     // check distance to target every frame:
29.     var distance = (target.position - myTransform.position).magnitude;
30.     
31.     if (distance < closeEnoughDistance)
32.     {
33.     animation.Play("ZombieAttack");
34.     }
35.     
36.     if (chasing) 
37.     {
38.         //rotate to look at the player
39.         myTransform.rotation = Quaternion.Slerp(myTransform.rotation,
40.         Quaternion.LookRotation(target.position - myTransform.position), rotationSpeed*Time.deltaTime);
41.  
42.         // give up, if too far away from target:
43.         if (distance > giveUpThreshold) 
44.         {
45.         chasing = false;
46.         }
47.         else if (distance > closeEnoughDistance)
48.         {
49.         myTransform.position += myTransform.forward * moveSpeed * Time.deltaTime;
50.         }
51.         else if (distance < attackThreshold && Time.time > attackRepeatTime) 
52.  
53.         {
54.         target.SendMessage("ApplyDamage",10);
55.         }
56.  
57.         attackTime = Time.time+ attackRepeatTime;
58.         }
59.         else 
60.         {
61.         // not currently chasing.
62.  
63.         // start chasing if target comes close enough
64.         if (distance < chaseThreshold) 
65.         {
66.         chasing = true;
67. }
68. }
69. }