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using UnityEngine;
using System.Collections;

public class LookAtFixed : MonoBehaviour {
	public Transform lookAt;
	
	void Update()
	{
		Vector3 worldLookDirection = lookAt.position - transform.position;
		Vector3 localLookDirection = transform.InverseTransformDirection(worldLookDirection);
		localLookDirection.y = 0;
		transform.forward = transform.rotation * localLookDirection;
	}
}

using UnityEngine;
using System.Collections;

public class LookAt : MonoBehaviour {
	public Transform lookAt;

	void Update() {
		transform.LookAt(lookAt);
	}
}