using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class PingPong : MonoBehaviour {

    public float distance;
    public float speed;
    float originalZ;

    // Use this for initialization
    void Start () {
        originalZ = this.transform.position.z;
    }

    // Update is called once per frame
    void Update () {

        if (this.transform.position.z > originalZ + distance) {
            speed *= -1;
        }
        if (this.transform.position.z < originalZ) {
            this.transform.position = new Vector3(this.transform.position.x,
                                                  this.transform.position.y,
                                                  originalZ);
            speed *= -1;
        }
        this.transform.Translate (Vector3.forward * speed * Time.deltaTime);
    }
}