private Initializable replaceSceneContent(String fxml) throws Exception {
        FXMLLoader loader = new FXMLLoader();
        InputStream in = getClass().getResourceAsStream(fxml);
        loader.setBuilderFactory(new JavaFXBuilderFactory());
        loader.setLocation(getClass().getResource(fxml));
        AnchorPane page;
        try {
            page = (AnchorPane) loader.load(in);
        } finally {
            in.close();
        } 
        Scene scene = new Scene(page, 600, 400);
        primaryStage.setScene(scene);
        primaryStage.sizeToScene();
        ScreenController ctrl;
        switch (fxml){
            case "Welcome":
                loader.setController(welcomeController);
                break;
            case "Configuration":
                loader.setController(configurationController);
                break;
            case "Universe":
                loader.setController(universeController);
                break;
            case "SolarSystem":
                loader.setController(solarSystemController);
                break;
            case "Planet":
                loader.setController(planetController);
                break;
        }
        return loader.getController();
    }