Update

src/main/java/MenuPanel.java

@@ -40,7 +40,7 @@ public class MenuPanel extends JPanel {
 
         public void keyPressed(KeyEvent e) {
             if (e.getKeyCode() == KeyEvent.VK_1) {
-                new PingPong.GamePanel();
+                new PingPong.GameFrame();
             }
             if (e.getKeyCode() == KeyEvent.VK_2) {
                 BShip game = new BShip();

src/main/java/PingPong/GameFrame.java

@@ -5,7 +5,7 @@ import java.awt.*;
 
 public class GameFrame extends JFrame {
     GamePanel panel;
-    GameFrame(){
+   public GameFrame(){
         panel = new GamePanel();
         this.add(panel);
         this.setTitle("2D Ping-Pong");