public static void loop(String filename) {
        URL url = null;
        try {
            File file = new File(filename);
            if (file.canRead()) url = file.toURI().toURL();
        }
        catch (MalformedURLException e) { e.printStackTrace(); }
        if (url == null) throw new RuntimeException("audio " + filename + " not found");
        AudioClip clip = Applet.newAudioClip(url);
        clip.loop();
    }