public float moveSpeed;
private Vector3 rotationSpeed;
public Camera cam;

public Vector3 straightForward;

public Quaternion spreadAngleRight;
public Quaternion spreadAngleLeft;

public Vector3 localRightVector;
public Vector3 localLeftVector;

public Vector3 newVectorRight;
public Vector3 newVectorLeft;

private Rigidbody rb;

Vector3 movement;
void Start () {
    rb = gameObject.GetComponent<Rigidbody> ();
    rotationSpeed = new Vector3(0, 100, 0);

    straightForward = transform.TransformDirection (Vector3.forward);

    spreadAngleRight = Quaternion.AngleAxis (45, new Vector3 (0, 1, 0));
    spreadAngleLeft = Quaternion.AngleAxis (315, new Vector3 (0, 1, 0));

    localRightVector = spreadAngleRight * straightForward;
    localLeftVector = spreadAngleLeft * straightForward;

    newVectorRight = transform.TransformDirection (localRightVector);
    newVectorLeft = transform.TransformDirection (localLeftVector);
}

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

    #region Control
    if(Input.GetKey(KeyCode.W)){
        rb.MovePosition(transform.position + transform.TransformDirection(Vector3.forward * moveSpeed) * Time.deltaTime);
    }
    if (Input.GetKey (KeyCode.A)) {
        rb.MovePosition(transform.position + transform.TransformDirection(-Vector3.right * moveSpeed) * Time.deltaTime);
    }
    if (Input.GetKey (KeyCode.S)) {
        rb.MovePosition(transform.position + transform.TransformDirection(-Vector3.forward * moveSpeed) * Time.deltaTime);
    }
    if (Input.GetKey (KeyCode.D)) {
        rb.MovePosition(transform.position + transform.TransformDirection(Vector3.right * moveSpeed) * Time.deltaTime);
    }
    if (Input.GetKey(KeyCode.W) && Input.GetKey(KeyCode.D)){
        rb.MovePosition(transform.position + transform.TransformDirection(newVectorRight * moveSpeed) * Time.deltaTime);
    }
    if (Input.GetKey(KeyCode.W) && Input.GetKey(KeyCode.A)){
        rb.MovePosition(transform.position + transform.TransformDirection(newVectorLeft * moveSpeed) * Time.deltaTime);
    }
    if (Input.GetKey(KeyCode.S) && Input.GetKey(KeyCode.D)){
        rb.MovePosition(transform.position - transform.TransformDirection(newVectorLeft * moveSpeed) * Time.deltaTime);
    }
    if (Input.GetKey(KeyCode.S) && Input.GetKey(KeyCode.A)){
        rb.MovePosition(transform.position - transform.TransformDirection(newVectorRight * moveSpeed) * Time.deltaTime);
    }
    Vector3 mouseInputX = Input.GetAxis ("Mouse X") * rotationSpeed;
    Vector3 mouseInputY = Input.GetAxis ("Mouse Y") * rotationSpeed;

    gameObject.transform.Rotate (mouseInputX * Time.deltaTime, Space.Self);
    cam.transform.LookAt(gameObject.transform.position + Vector3.up * 2f);

    #endregion
}