Renderer.java

import javax.swing.JFrame;
import javax.swing.JPanel;
import java.awt.Graphics;
import java.awt.Color;
import javax.imageio.ImageIO;
import java.awt.image.BufferStrategy;
import java.awt.Graphics2D;
import java.awt.Canvas;
import java.awt.Dimension;

public class Renderer extends JPanel {
    boolean screen[] = new boolean[64 * 32];
    int factor;

    Renderer(int width, int height) {
        this.setPreferredSize(new Dimension(width, height));
        this.setVisible(true);
        factor = width/64;

        for (int i = 0; i < 64*32; i++) {
            screen[i] = false;
        }
    }

    void clear() {
        for (int i = 0; i < 64*32; i++) {
            screen[i] = false;
        }
    }

    boolean setPixel(byte x, byte y, boolean set) {
        boolean old = screen[((y%32) * 64) + (x%64)];
        screen[((y%32) * 64) + (x%64)] ^= set;
        return old && !screen[((y%32) * 64) + (x%64)];
    }

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

        for (int x = 0; x < 64; x++) {
            for (int y = 0; y < 32; y++) {
                int pixelPos = (y * 64) + x;

                if (screen[pixelPos]) {
                    g.setColor(Color.BLACK);
                    g.fillRect(x*factor, y*factor, factor, factor);
                }

                else {
                    g.setColor(Color.WHITE);
                    g.fillRect(x*factor, y*factor, factor, factor);
                }
            }
        }
    }
}