import java.awt.*;
import java.applet.*;
import java.awt.event.*;

public class Fireflies extends Applet implements Runnable {
	
	Firefly fireflies[] = new Firefly[100];
	
	// Double buffering initialization
	private Dimension appletSize;
	private Image offscreenBuffer;
   	public Graphics gOff, g;
		
	private Image moon;
		
	private Thread runMe;
	
	public void init() {
		
		// Set up the double buffering.
		g = getGraphics();
		appletSize = getSize();
		
		offscreenBuffer = createImage(appletSize.width, appletSize.height);
       		gOff = offscreenBuffer.getGraphics();
		moon = getImage(getDocumentBase(), "moon.gif");

		// Wait for image load
		// Pass media tracker any component (such as a canvas or an applet)
		MediaTracker tracker = new MediaTracker(this);
		
		// Add images
		tracker.addImage (moon, 0);
		
		// Wait for images
		try {
			tracker.waitForAll();
		} catch (InterruptedException ie) {}
		
		// Create fireflies
		for (int i=0; i < fireflies.length; i++)
			fireflies[i] = new Firefly(appletSize.width, appletSize.height-300 - (int)(Math.random()*150));
			
		runMe = new Thread(this);
		runMe.start();
	}
	
 	public void run() {

		while (true) {
	
			gOff.setColor(Color.black);
			gOff.fillRect(0,0, appletSize.width, appletSize.height);

			gOff.drawImage(moon, (appletSize.width-256) / 2, 32, null);	

			gOff.setColor(Color.yellow);
			for (int i=0; i < fireflies.length; i++) {
				
				fireflies[i].updatePos();
				
				if (fireflies[i].visible) {
					gOff.setColor(fireflies[i].color);
					gOff.fillRect((int)fireflies[i].x, (int)fireflies[i].y+320, fireflies[i].size, fireflies[i].size);
				}
			}
			
			paint(g);

			try {runMe.sleep(5);}
			catch (InterruptedException e) {return; }
		}
	}
	
 	public void paint(Graphics g) {
		// Blit the buffer
		g.drawImage(offscreenBuffer, 0, 0, null);
	}
}

class Firefly {
	
	double x, y;
	double dX, dY;
	double speed = 1.0;
	double biasAmount = .225;
	Color color;
	
	int xRange, yRange;
	int size;
	
	int lightInterval;
	boolean visible;
	
	public Firefly(int xRange, int yRange) {
		
		this.xRange = xRange; this.yRange = yRange;
		
		x = Math.random() * xRange;
		y = Math.random() * yRange;

		dX = (Math.random() * speed - speed / 2.0f) * .8f;
		dY = (Math.random() * speed - speed / 2.0f) * .5f;
		
		if (Math.random() > .5)
			visible = true;
		else 
			visible = false;
		
		if (Math.random() > .5)
			size = 1;
		else 
			size = 2;
		
		lightInterval = (int)(Math.random() * 60);
		
		int shade = (int)(Math.random() * 128 + 128);
		int greenShade = (int)(Math.random() * 15);
		if (greenShade + shade <= 255) greenShade = greenShade + shade;
		color = new Color(greenShade, shade, 0);
	}
	
	public void updatePos() {
		
		double denom = 1;

		if (size == 1) denom = 2;
		
		x += dX / denom;
		y += dY / denom;
		
		// Add some directional bias
		double ddX = Math.random() * biasAmount - biasAmount / 2.0;
		double ddY = Math.random() * biasAmount - biasAmount / 2.0;
		
		if (ddX + dX < speed && ddX + dX > 0) dX += ddX;
		if (ddY + dY < speed / 2.0 && ddY + dY > 0) dY += ddY;
		
		// Make sure they stay on screen
		if (x > xRange) {
			x -= xRange;
			visible = false;
		}
		
		if (x < 0) {
			x += xRange;
			visible = false;
		}
		
		if (y > yRange) {
			y -= yRange;
			visible = false;
		}
		
		if (y < 0) {
			
			if (Math.random() < .02) {
				y += yRange;
				visible = false;
			}
		}
		
		// Make them blink in and out
		if (visible) {
			
			lightInterval--;
			
			if (lightInterval <= 0) {
				visible = false;
				lightInterval = (int)(Math.random() * 30) + 90;
			}
		} else {
			lightInterval--;
			
			if (lightInterval <= 0) {
				visible = true;
				lightInterval = (int)(Math.random() * 30) + 90;
			}	
		}
	}
}