BorderPane not showing other pane except for center Javafx

I have this piece of code here that has a borderpane as a parent and 2 other panes, one is a minesweeper game and the other is an empty pane with a black background, the minesweeper game is set to be in the center of the borderpane and the empty pane is set to be in the bottom. Right now when I run the code, it will only show the minesweeper game and not the empty pane (can be seen in the image). How do I make it show the empty pane at the bottom of the borderpane?

(Layout as of right now)

package project;

import java.util.ArrayList;
import java.util.List;

import javafx.application.Application;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.Pane;
import javafx.scene.layout.StackPane;
import javafx.scene.paint.Color;
import javafx.scene.shape.Rectangle;
import javafx.scene.text.Font;
import javafx.scene.text.Text;
import javafx.stage.Stage;

public class MinesweeperApp extends Application {

    private static final int TILE_SIZE = 40;
    private static final int W = 800;
    private static final int H = 800;

    private static final int X_TILES = W / TILE_SIZE;
    private static final int Y_TILES = H / TILE_SIZE;

    private Tile[][] grid = new Tile[X_TILES][Y_TILES];
//    private ArrayList[][] grid = new ArrayList[X_TILES][Y_TILES];
    private Scene scene;

    private Parent createContent() {
        BorderPane root = new BorderPane();
        Pane middlepane = new Pane();
        Pane lowerPane = new Pane();
        

        lowerPane.setStyle("-fx-background-color: black;");
        root.setTop(lowerPane);
        root.setBottom(middlepane);
        middlepane.setPrefSize(W, H);

        for (int y = 0; y < Y_TILES; y++) {
            for (int x = 0; x < X_TILES; x++) {
                Tile tile = new Tile(x, y, Math.random() < 0.2);

                grid[x][y] = tile;
                middlepane.getChildren().add(tile);
            }
        }

        for (int y = 0; y < Y_TILES; y++) {
            for (int x = 0; x < X_TILES; x++) {
                Tile tile = grid[x][y];

                if (tile.hasBomb)
                    continue;

                long bombs = getNeighbors(tile).stream().filter(t -> t.hasBomb).count();

                if (bombs > 0)
                    tile.text.setText(String.valueOf(bombs));
            }
        }

        return root;
    }

    private List<Tile> getNeighbors(Tile tile) {
        List<Tile> neighbors = new ArrayList<>();

        // ttt
        // tXt
        // ttt

        int[] points = new int[] {
                -1, -1,
                -1, 0,
                -1, 1,
                0, -1,
                0, 1,
                1, -1,
                1, 0,
                1, 1
        };

        for (int i = 0; i < points.length; i++) {
            int dx = points[i];
            int dy = points[++i];

            int newX = tile.x + dx;
            int newY = tile.y + dy;

            if (newX >= 0 && newX < X_TILES
                    && newY >= 0 && newY < Y_TILES) {
                neighbors.add(grid[newX][newY]);
            }
        }

        return neighbors;
    }

    private class Tile extends StackPane {
        private int x, y;
        private boolean hasBomb;
        private boolean isOpen = false;

        private Rectangle border = new Rectangle(TILE_SIZE - 2, TILE_SIZE - 2);
        private Text text = new Text();

        public Tile(int x, int y, boolean hasBomb) {
            this.x = x;
            this.y = y;
            this.hasBomb = hasBomb;

            border.setStroke(null);
            border.setFill(Color.NAVY);

            text.setFont(Font.font(18));
            text.setText(hasBomb ? "X" : "");
            text.setVisible(false);

            getChildren().addAll(border, text);

            setTranslateX(x * TILE_SIZE);
            setTranslateY(y * TILE_SIZE);

            setOnMouseClicked(e -> open());
        }

        public void open() {
            System.out.println("clicked");
            System.out.println("x: " + this.x + " " + "y: " + this.y);
            if (isOpen){
                return;
            }



            if (hasBomb) {
                System.out.println("Game Over");
                scene.setRoot(createContent());
                return;
            }

            isOpen = true;
            text.setVisible(true);
            border.setFill(Color.RED);

            if (text.getText().isEmpty()) {
                getNeighbors(this).forEach(Tile::open);
            }
        }
    }

    @Override
    public void start(Stage stage) throws Exception {
        scene = new Scene(createContent());
        stage.setScene(scene);
        stage.show();
    }

    public static void main(String[] args) {

        launch(args);
    }
}