I’ve been making a 2D java game for a history project, but rectangles randomly stoped being drawn

The code:

import java.awt.Color;
import javax.swing.JFrame;
public class Main {
    public static void main(String[] args){
        JFrame jf = new JFrame();
        Game g = new Game();
        g.play = true;
        jf.setBackground(Color.black);
        jf.setTitle("History");
        jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        jf.setBounds(10, 10, 800, 600);
        jf.setResizable(false);
        jf.setAlwaysOnTop(true);
        jf.setVisible(true);
        jf.add(g);
    }
}

second class:

import javax.swing.*;
import java.awt.event.*;
import java.awt.*;

public class Game extends JPanel implements KeyListener, ActionListener, MouseListener{
    public boolean play = false;
    private static boolean clickHold = false;
    private boolean start = true;

    public Game(){
        addKeyListener(this);
        addMouseListener(this);
        setFocusable(true);
        Timer timer = new Timer(5, this);
        timer.start();
    }

    @Override
    protected void paintComponent(Graphics g){
        super.paintComponent(g);

        if(start){
            start = false;
            g.setColor(Color.black);
            g.drawRect(0, 0, 1000, 1000);

            g.setColor(Color.WHITE);
            g.setFont(new Font("serif", Font.BOLD, 50));
            g.drawString("Copernicus Simulator 9000", 200, 200);
        }
    }

    @Override
    public void mouseClicked(MouseEvent e) {
        clickHold = true;
    }

    @Override
    public void mouseReleased(MouseEvent e) {
        clickHold = false;
    }

    @Override
    public void mouseEntered(MouseEvent e) {
    }

    @Override
    public void mouseExited(MouseEvent e) {
    }

    @Override
    public void mousePressed(MouseEvent e) {
    }

    @Override
    public void keyPressed(KeyEvent e) {
    }

    @Override
    public void keyReleased(KeyEvent e) {
    }

    @Override
    public void keyTyped(KeyEvent e) {
    }

    @Override
    public void actionPerformed(ActionEvent e) {

    }
}

is there any reason that the rectangles are not drawing?
when i run the code, it simply displays a empty white window.
if anyone could answer this, it would help me a bunch.
P.S. It would be great if this was answered sooner that later