Unity - Space Ship Code

using UnityEngine;
using System.Collections;

public class PlayerMovement : MonoBehaviour {

    Animator anim;

    public float maxSpeed = 5f;
    public float rotSpeed = 180f;
    float sensitivity;
    float shipBoundRadius = 0.5f;
    bool isMoveing = false;


    // Use this for initialization
    void Start () {

        anim = GetComponent<Animator> ();

    }

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

        //ROTATE Ship

        // Get Rotation Quaternion
        Quaternion rotation = transform.rotation;

        // Grab Z Euler Angle
        float z = rotation.eulerAngles.z;

        // Change Angle When Inputed
        z -= Input.GetAxis ("Horizontal") * rotSpeed * Time.deltaTime;

        // Make a new Quaternion with X = 0, Y = 0, Z = Our Angle
        rotation = Quaternion.Euler (0, 0, z);

        //Set rotation
        transform.rotation = rotation;


        //Input.GetAxis - 0 if not 0.num to 1 if forward -num if back
        //Transform is pos rotatation and scale

        Vector3 pos = transform.position;
        Vector3 velocity = new Vector3( 0,  Input.GetAxis("Vertical") * maxSpeed * Time.deltaTime,  0);

        float screenRatio = (float) Screen.width / (float) Screen.height;
        float mWidth = Camera.main.orthographicSize * screenRatio;

        if (pos.y > (Camera.main.orthographicSize+shipBoundRadius)) {
            pos.y = -Camera.main.orthographicSize;
        }
        else if (pos.y < -(Camera.main.orthographicSize+shipBoundRadius)) {
            pos.y = Camera.main.orthographicSize;
        }

        if (pos.x > (mWidth+shipBoundRadius)) {
            pos.x = -mWidth;
        }
        else if (pos.x < -(mWidth+shipBoundRadius)) {
            pos.x = mWidth;
        }

        pos += rotation * velocity;

        transform.position = pos;

    }
}