Given the following code, could someone help me to implement some extra functionality:

// DrawingGUI.java

import javafx.application.Application;

import static javafx.application.Application.launch;

import javafx.beans.value.ChangeListener;

import javafx.beans.value.ObservableValue;

import javafx.geometry.Pos;

import javafx.scene.Scene;

import javafx.scene.control.Button;

import javafx.scene.control.ComboBox;

import javafx.scene.input.MouseEvent;

import javafx.scene.layout.HBox;

import javafx.scene.layout.Pane;

import javafx.scene.layout.VBox;

import javafx.scene.paint.Color;

import javafx.scene.shape.Line;

import javafx.scene.text.Font;

import javafx.scene.text.Text;

import javafx.stage.Stage;

public class DrawingGUI extends Application {

//array of color names for listing in combobox

final String colors[] = {"Red", "Green", "Blue"};

//declaring UI elements

Pane drawingSpace;

boolean drawing = false;

double currentX, currentY;

Text penStatus;

ComboBox colorBox;

Button clear;

Color selectedColor = Color.RED; //default color

@Override

public void start(Stage primaryStage) {

//defining all the controls

penStatus = new Text("Pen: Off");

penStatus.setFont(new Font(20));

colorBox = new ComboBox();

colorBox.getItems().addAll(colors);

colorBox.setValue("Red");

clear = new Button("Clear");

//adding controls into an HBox (horizontal) and aligning center

HBox hBox = new HBox(penStatus, colorBox, clear);

hBox.setSpacing(10);

hBox.setAlignment(Pos.CENTER);

//creating a pane for drawing area

drawingSpace = new Pane();

drawingSpace.setMinSize(500, 500);

//creating a Vbox to arrange hbox and drawing area vertically

VBox box = new VBox(hBox, drawingSpace);

Pane root = new Pane(box);

//adding mouse event listeners

drawingSpace.addEventFilter(MouseEvent.MOUSE_CLICKED, e -> {

//changing drawing to false if true, true if false

if (drawing) {

drawing = false;

penStatus.setText("Pen: Off");

} else {

drawing = true;

currentX = e.getX();

currentY = e.getY();

penStatus.setText("Pen: On");

}

});

drawingSpace.addEventFilter(MouseEvent.MOUSE_MOVED, e -> {

//if drawing, creating a line from previous point to the new point

if (drawing) {

double x = e.getX();

double y = e.getY();

Line line = new Line(currentX, currentY, x, y);

line.setFill(selectedColor);

line.setStroke(selectedColor);

//adding to the drawing space

drawingSpace.getChildren().add(line);

currentX = x;

currentY = y;

}

});

//adding change listener for color combo box

colorBox.valueProperty().addListener(new ChangeListener() {

@Override

public void changed(ObservableValue ov, String t, String t1) {

//updating selected color

if (colorBox.getValue().equalsIgnoreCase("Red")) {

selectedColor = Color.RED;

} else if (colorBox.getValue().equalsIgnoreCase("Green")) {

selectedColor = Color.GREEN;

} else {

selectedColor = Color.BLUE;

}

}

});

//adding action listenr for resetting drawing space

clear.setOnAction(e -> {

drawingSpace.getChildren().clear();

});

Scene scene = new Scene(root, 500, 500);

primaryStage.setScene(scene);

primaryStage.show();

}

public static void main(String[] args) {

launch(args);

}

}

Extra Credit A: Add support for an eraser. When the eraser is activated, the user can remove previously drawn points from the drawing space. For full extra credit, the points should actually be removed (not just "covered up") To complete this extra credit, add a third state for the pen: it is now draw/off/erase. (Hint: consider using an enum!) Hint: use an iterator and check out the "contains" method in the Node class! Extra Credit B: Add an additional drawing functionality. This must be different from simply choosing another pen color- that will not count for any extra credit. Be creative