void AsteroidDestroid()
    {
        //crear la moneda, añadir el score y mostrarlo por pantalla
        Instantiate(coin, transform.position, transform.rotation);
        scoreText.GetComponent <TextMesh>().text = "+" + scoreValue;
        Instantiate(scoreText, transform.position, scoreText.transform.rotation);

        if (gameController.missionLevel == false)
        {
            gameController.AddScore(scoreValue);
        }
        else
        {
            gameController.AddScoreMision();
        }

        Destroy(gameObject);
    }