A tiny invaders game that fits into 1kB of pack200 jar file.

InvadersMustDie.java

import java.awt.Canvas;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.awt.image.BufferStrategy;
import java.util.Random;
import javax.swing.JApplet;

public class M extends JApplet implements Runnable, KeyListener {
	boolean key[] = new boolean[65535];
	BufferStrategy strategy;
	Random r = new Random();

	@Override
	public void init() {
		setIgnoreRepaint(true);
		Canvas canvas = new Canvas();
		add(canvas);
		canvas.setBounds(0, 0, 800, 600);
		canvas.createBufferStrategy(2);
		strategy = canvas.getBufferStrategy();
		canvas.addKeyListener(this);
		new Thread(this).start();
	}

	public void run() {
		outer: while (true) {
			boolean gameover = false;
			int shipPos = 400;
			int shotX = 400; int shotY = 550;
			boolean[] iAlive = new boolean[20];
			int[] iX = new int[20];
			int iY = 0;
			int level = 0;
			int dir = 0;

			game: while (true) {
				try { Thread.sleep(20); } catch (Exception ex) {}

				Graphics g = strategy.getDrawGraphics();

				if (key[KeyEvent.VK_LEFT]) { shipPos -= 5; }
				if (key[KeyEvent.VK_RIGHT]) { shipPos += 5; }
				if (shipPos < 10) { shipPos = 10; }
				if (shipPos > 790) { shipPos = 790; }

				if (shotY < 0) { shotY = 550; }
				if (shotY == 550) {
					shotX = shipPos;
					if (key[KeyEvent.VK_SPACE]) { shotY = 549; }
				} else {
					shotY -= 10;
				}

				g.setColor(Color.BLACK);
				g.fillRect(0, 0, 800, 600);

				g.setColor(Color.RED);

				if (gameover) { g.drawString("GAME OVER", 100, 100); }

				g.fillRect(shotX - 1, shotY, 3, 20);

				g.setColor(Color.GREEN);
				if (r.nextInt(100 - level) == 0) {
					dir = r.nextBoolean() ? -2 - level / 10 : 2 + level / 10;
				}
				for (int i = 0; i < level; i++) {
					if (iAlive[i]) {
						if (shotY != 550 && Math.abs(iX[i] - shotX) < 20 && Math.abs(iY - shotY) < 20) {
							iAlive[i] = false;
							shotY = 550;
							continue;
						}
						if (iX[i] < 0 || iX[i] > 800) { dir = -dir; }
						g.fillOval((iX[i] += dir) - 15, iY - 15, 30, 30);
					}
				}

				iY += 1 + level / 30;

				g.setColor(Color.LIGHT_GRAY);
				g.fillOval(shipPos - 10, 530, 20, 40);

				strategy.show();
				if (gameover) { try { Thread.sleep(2000); } catch (Exception e) {} continue outer; }

				for (boolean alive : iAlive) {
					if (alive) {
						if (iY > 600) {
							gameover = true;
						}
						continue game;
					}
				}
				level++;
				for (int i = 0; i < level; i++) {
					iAlive[i] = true;
					iX[i] = r.nextInt(800);
					iY = 0;
				}
			}
		}
	}

	public void keyTyped(KeyEvent e) {}

	public void keyPressed(KeyEvent e) {
		key[((KeyEvent) e).getKeyCode()] = true;
	}

	public void keyReleased(KeyEvent e) {
		key[((KeyEvent) e).getKeyCode()] = false;
	}
}