Add MainFrame class.

src/MainFrame.java

+import javax.swing.*;
+import java.awt.*;
+import java.awt.event.ActionEvent;
+import java.awt.event.ActionListener;
+import java.awt.event.MouseAdapter;
+import java.awt.event.MouseEvent;
+
+public class MainFrame extends JFrame {
+
+    private ImageIcon mainPhotoIcon;
+    private ImageIcon offlineModeIcon;
+    private ImageIcon onlineModeIcon;
+    private ImageIcon settingIcon;
+    private ImageIcon exitIcon;
+    private JButton offlineModeButton;
+    private JButton onlineModeButton;
+    private JButton settingButton;
+    private JButton exitButton;
+    private JLabel mainPhoto;
+    private JPanel items;
+
+    public MainFrame() {
+
+        setBackground(Color.WHITE);
+        setResizable(false);
+        setLayout(new BorderLayout());
+        setBounds(500, 200, 700, 660);
+
+        mainPhotoIcon = new ImageIcon("gifFiles/tank.gif");
+        mainPhoto = new JLabel(mainPhotoIcon);
+
+        items = new JPanel();
+        items.setBackground(Color.WHITE);
+        items.setLayout(new FlowLayout());
+
+        //initButtons();
+
+        add(items, BorderLayout.CENTER);
+        add(mainPhoto, BorderLayout.NORTH);
+        setVisible(true);
+    }
+}
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