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

public class BinomialFall extends Applet implements Runnable {

  Thread thread; 
  Ball green, red, purple;
  Image needle;
//  int late = 0;
  boolean started = false;

  Image appletImg;
  Graphics appletG;

//  public void init() {
//  }

  public void start() {
    appletImg = createImage(size().width, size().height);
    appletG = appletImg.getGraphics();

    green = new Ball("green", getImage(getDocumentBase(), "greenball.gif"), this, getBackground());
    red = new Ball("red", getImage(getDocumentBase(), "redball.gif"), this, getBackground());
    purple = new Ball("purple", getImage(getDocumentBase(), "purpleball.gif"), this, getBackground());
    needle = getImage(getDocumentBase(), "blackball.gif");
  
    started = true;
    drawBackground(appletG);

    if(thread == null) {
      thread = new Thread(this);
      thread.start();
    }
//    repaint();
  }

  public void stop() {
    if(thread != null) {
      thread.stop();
      thread = null;
    }
  }
  
  public void run() {
    while(thread != null) {
      repaint();
      try { thread.sleep(300); }
      catch (InterruptedException e) {}
    }
  }  

  public void update(Graphics g) {
    drawBackground(appletG);
    green.move(appletG);
//    if (late++ > 5)
    red.move(appletG);
    purple.move(appletG);
//    if(late > 6) late = 6;
    paint(g);
  }

  public void drawBackground(Graphics g) {
    int level;
    int x = 0,y = 0,i,j;
    int u = 25;
    int margin;
  
    Rectangle r = bounds();
  
    g.setColor(getBackground());
    g.fillRect(0,0, r.width, r.height);
    g.setColor(getForeground());
  
    g.drawRect(0,0, r.width - 1, r.height - 1);
    if (r.height < r.width) {
      level = (r.height - 4*u)/u;
    } else {
      level = (r.width - u)/(2*u);
    }
    margin = (r.width - (level)*2*u)/2;
    for (j = r.height - 2*u; j > 2*u; j -= u, margin += u) {
      for (i = margin; i < r.width - margin - u; i += 2*u) {
        x = i; y = j;
        g.drawImage(needle, x, y, this);
      }
    }
  
    if (started) {
      started = false;
  
      green.setdelta(u,u);
      green.setVars(x, y, level, 0);
      green.move(g);
  
      red.setdelta(u,u);
      red.setVars(x, y, level, 2);
      red.move(g);
  
      purple.setdelta(u,u);
      purple.setVars(x, y, level, 4);
      purple.move(g);
  
//      late = 0;
    };
  }

  public void paint(Graphics g) {
    g.drawImage(appletImg, 0, 0, this);
  }
  
}