private void paintNaves(Graphics2D g2d){
        int nNaves = juego.getnNaves();
        List<Nave> nav=naves;
        List<Nave> list = (nNaves==2) ? nav : nav.subList(0, 1);        
        for (Nave n : list) {
            if(n.isVivo()) n.paint(g2d);
        }
    }