Need help on converting code for 3D code for 2D.

Code (CSharp):

1. using UnityEngine;
2. using System.Collections;
3.  
4. public class EnemyLook : MonoBehaviour {
5.     public Transform playerPosition;
6.     public Quaternion rotationAngleX;
7.     public float TurnSpeed = 5;
8.     // Use this for initialization
9.     void Start () {
10.    
11.     }
12.    
13.     // Update is called once per frame
14.     void Update () {
15.         rotationAngleX = Quaternion.LookRotation(playerPosition.position - transform.position);
16.         transform.rotation = Quaternion.Slerp(transform.rotation, rotationAngleX, Time.deltaTime * TurnSpeed);
17.     }
18. }
19.  

This does work just great, but works on 3D plane, while I work on 2D game.
I just barely worked out to get it working, I seriously have no idea how to get it on 2D plane.

 

This code can be achieved by:

Code (CSharp):

1.  Quaternion rotation = Quaternion.LookRotation
2.              (Target.transform.position - transform.position, transform.TransformDirection(Vector3.up));
3.          transform.rotation = new Quaternion(0, 0, rotation.z, rotation.w);