Unity - Di chuyen va xoay theo click chuot

using UnityEngine;
using System.Collections;

public class theLastOneBehaviour : MonoBehaviour {

    private Vector3 clickPos;  // vi tri click left mouse
    public float speed = 5.0f;

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

    // Update is called once per frame
    void Update () {
        MovetheLastOne ();
        Rotation();
    }

    void MovetheLastOne(){
        // bat su kien click chuot trai
        if (Input.GetMouseButton (0)) {
            // Camera.main.ScreenToWorldPoint --> Chuyen Toa do man hinh thanh toa do 3 chieu
            // Input.mousePosition --> Lay toa do man hinh
            clickPos = Camera.main.ScreenToWorldPoint(Input.mousePosition);
            // giu toa do z
            clickPos.z = transform.position.z;
        }

        // di chuyen tu vi tri hien tai toi clickPos
        transform.position = Vector3.MoveTowards (transform.position, clickPos, Time.deltaTime * speed);
    }

    void Rotation(){
        // vi tri click chuot tren man hinh
        Vector3 screenPos = Input.mousePosition;
        // doi sang tao do chieu 3 chieu
        Vector3 worldPos = Camera.main.ScreenToWorldPoint (screenPos);

        float dx = transform.position.x - worldPos.x; // do lech truc x
        float dy = transform.position.y - worldPos.y; // do lech truc y

        float radAngle = Mathf.Atan2 (dy, dx);
        float degAngle = radAngle * Mathf.Rad2Deg; // doi radian sang degree (do)
        // xoay - Tinh Quaternion
        Quaternion qua = Quaternion.Euler (new Vector3(0,0,degAngle+90));
        transform.rotation = qua;
    }
}