private Rigidbody rb;

    // Use this for initialization
    void Start () {
        rb = GetComponent<Rigidbody>();
    }

    // Update is called once per frame
    void FixedUpdate () {
        float moveHorizontal = Input.GetAxis ("Horizontal");
        float moveVertical = Input.GetAxis ("Vertical");

        Vector3 movement = new Vector3 (moveHorizontal, 0.0f, moveVertical);

        rb.AddForce (movement);
    }