PlayerController - Space Shooter

using UnityEngine;
using System.Collections;

[System.Serializable]
public class Boundary
{
    public float xMin, xMax, zMin, zMax;
}

public class PlayerController : MonoBehaviour
{
    public float speed;

    public float tilt;
    public Boundary boundary;

    public GameObject shot;
    public Transform shotSpawn;

    public float fireRate;
    private float nextFire;
    void Update()
    {
        //Input.GetButton
        //Instantiate(shot, shotSpawn.position, shotSpawn.rotation);
        if (Input.GetButton("Fire1") && Time.time > nextFire) {
            nextFire = Time.time + fireRate;
            Instantiate(shot, shotSpawn.position, shotSpawn.rotation);
            audio.Play();


        };

        /*
        if (Input.GetButton("Fire2") && Time.time > nextFire) {
            nextFire = Time.time + fireRate;
            Instantiate(shot, shotSpawn.position, shotSpawn.rotation);
            audio.Play();
        }
        */
    }

    void FixedUpdate ()
    {
        float moveHorizontal = Input.GetAxis ("Horizontal");
        float moveVertical = Input.GetAxis ("Vertical");

        Vector3 movement = new Vector3 (moveHorizontal, 0.0f, moveVertical);
        rigidbody.velocity = movement * speed;

        // bang chuot
        Vector3 mousePos = Camera.main.ScreenToWorldPoint(Input.mousePosition);
        transform.position = Vector3.Lerp(transform.position, mousePos, Time.deltaTime * speed);

        // di chuyen bang cam bien
        /*
        Vector3 direction = Vector3.zero;
        direction.x = -Input.acceleration.z;
        direction.z = Input.acceleration.y;
        //* Time.deltaTime
        transform.Translate (direction * speed);
        */

        rigidbody.position = new Vector3
            (
                Mathf.Clamp (rigidbody.position.x, boundary.xMin, boundary.xMax),
                0.0f,
                Mathf.Clamp (rigidbody.position.z, boundary.zMin, boundary.zMax)
                );

        rigidbody.rotation = Quaternion.Euler (0.0f, 0.0f, rigidbody.velocity.x * -tilt);
    }

}