exit

SleekCanvas.java

        addWindowListener(new WindowAdapter() {
            @Override
            public void windowClosing(WindowEvent e) {
                Runtime.getRuntime().addShutdownHook(new Thread() {
                    public void run() {
                        Runtime.getRuntime().halt(0);
                    }
                });
                Gdx.app.exit();
            }
        });