void Start () {
rb = this.GetComponent<Rigidbody> ();
randomDirection = new Vector3 (Random.Range(-1.0f, 1.0f), Random.Range (-1.0f, 1.0f), 0.0f);
randomSpeed = Random.value * 300.0f;
//transform.Rotate (randomDirection);
rb.AddForce (randomDirection * randomSpeed);
}