// esite.java - from bodytag.org's esite

import java.applet.Applet;
import java.awt.*;
import java.awt.event.*;
import java.awt.image.DirectColorModel;
import java.awt.image.MemoryImageSource;
import java.io.PrintStream;

public class esite extends Applet
   implements Runnable, MouseListener, MouseMotionListener
{  DirectColorModel  _dcm;
   MemoryImageSource _mis;
   Image    _img;
   int      _pxl [];
   particle _part [];
   int      _sprCol, _nPart, _nCyc, _rV, _gV;
   int      _w, _h, _wh, _cX, _cY, _bgCol;
   Thread   _thr;

   public void addPxl (int p, int j)
   { char c = '\374';
     int r0 = _pxl [p] & 0xFF0000;
     int g0 = _pxl [p] & 0xFF00;
     int b0 = _pxl [p] & 0xFF;
     int r1 = j        & 0xFF0000;
     int g1 = j        & 0xFF00;
     int b1 = j        & 0xFF;
     int r2 = (c * (r0 - r1) >> 8) + r1 & 0xFF0000;
     int g2 = (c * (g0 - g1) >> 8) + g1 & 0xFF00;
     int b2 = (c * (b0 - b1) >> 8) + b1 & 0xFF;
      _pxl [p] = r2 | g2 | b2;
   }

   public void drawLn (int x1, int y1, int x2, int y2, int c)
   { int  yD = y2 - y1;
     int  xD = x2 - x1;
     int  i;
     byte b;
      if (yD < 0) {yD = -yD;   i = -_w;} else {i = _w;}
      if (xD < 0) {xD = -xD;   b =  -1;} else {b =  1;}
      yD <<= 1;   xD <<= 1;   y1 *= _w;   y2 *= _w;
      addPxl (x1 + y1, c);
      if (xD > yD) {
        int d1 = yD - (xD >> 1);
         while (x1 != x2) {
            if (d1 >= 0) {y1 += i;  d1 -= xD;}
            x1 += b;   d1 += yD;   addPxl (x1 + y1, c);
         }
      }
      else {
        int d2 = xD - (yD >> 1);
         while (y1 != y2) {
            if (d2 >= 0) {x1 += b;  d2 -= yD;}
            y1 += i;   d2 += xD;   addPxl (x1 + y1, c);
         }
      }
   }

   public int byt (int i)
   {  if (i < 0) i = 0;   if (i > 255) i = 255;   return i;  }


   public void run ()   {while (_thr != null)  repaint ();}

   public void start ()
   {  if (_thr == null) {_thr = new Thread ();   _thr.start ();}  }

   public void stop ()  {_thr = null;}


   public void update (Graphics g)
   { int xMin = _w, yMin = _h, xMax = 0, yMax = 0, i1, p;

   // _rV += -2..3  limit at -10..10    ditto for _gV
      _rV += (int)(Math.random () * 5D) - 2;
      if (_rV > 10) _rV = 10;  else if (_rV < -10) _rV = -10;
      _gV += (int)(Math.random () * 5D) - 2;
      if (_gV > 10) _gV = 10;  else if (_gV < -10) _gV = -10;
      i1 = byt ((_sprCol >> 16) + _rV);
      _sprCol = i1 << 16 | i1 << 8 | i1;

   // _cX += -7..8  limit at 0.._w    ditto for _cY
      _cX += (int)(Math.random () * 15D) - 7;
      _cY += (int)(Math.random () * 15D) - 7;
      if (_cX < 0) _cX = 0;   if (_cX > _w) _cX = _w;
      if (_cY < 0) _cY = 0;   if (_cY > _h) _cY = _h;

      for (p = 1; p < _nPart; p++) {

      // draw part's line
        int x1 = (int)_part [p].x;
        int y1 = (int)_part [p].y;
        int x2 = (int)_part [p].lastx;
        int y2 = (int)_part [p].lasty;
         drawLn (x1, y1, x2, y2, _sprCol);

      // expand bounding rect
         if (x1 < xMin) xMin = x1;   if (x1 > xMax) xMax = x1;
         if (x2 < xMin) xMin = x2;   if (x2 > xMax) xMax = x2;
         if (y1 < yMin) yMin = y1;   if (y1 > yMax) yMax = y1;
         if (y2 < yMin) yMin = y2;   if (y2 > yMax) yMax = y2;

      // next spot
        double dx = (double)_cX - _part [p].x;
        double dy = (double)_cY - _part [p].y;
        double dl = Math.sqrt (dx * dx + dy * dy) + (double)(p * 3);
         _part [p].xvel  = (_part [p].xvel + dx / dl) * 0.96D;
         _part [p].yvel  = (_part [p].yvel + dy / dl) * 0.96D;
         _part [p].lastx = _part [p].x;
         _part [p].lasty = _part [p].y;
         _part [p].x    += _part [p].xvel;
         _part [p].y    += _part [p].yvel;
         if      (_part [p].x > (double)_w)
            {_part [p].x = _w - 1;  _part [p].xvel = 0.0D;}
         else if (_part [p].x < 0.0D)
            {_part [p].x = 0.0D;    _part [p].xvel = 0.0D;}
         if      (_part [p].y > (double)_h)
            {_part [p].y = _h - 1;  _part [p].yvel = 0.0D;}
         else if (_part [p].y < 0.0D)
            {_part [p].y = 0.0D;    _part [p].yvel = 0.0D;}
      }
      if (_nCyc == 100) {   // every 100 updates, dim it ?
         for (p = 0; p < _wh; p++) {
           char c = '\365';
           char c1 = '\377';
           int  r0 = _pxl [p] & 0xFF0000;
           int  g0 = _pxl [p] & 0xFF00;
           int  b0 = _pxl [p] & 0xFF;
           int  r1 = 0xFF0000;
           int  g1 = 0xFF00;
           int  r2 = (c * (r0 - r1) >> 8) + r1 & 0xFF0000;
           int  g2 = (c * (g0 - g1) >> 8) + g1 & 0xFF00;
           int  b2 = (c * (b0 - c1) >> 8) + c1 & 0xFF;
            _pxl [p] = r2 | g2 | b2;
         }
         _nCyc = 0;   xMin = 0;   yMin = 0;   xMax = _w;   yMax = _h;
      }
      _mis.newPixels (xMin, yMin, xMax - xMin, yMax - yMin);
      g.drawImage (_img, 0, 0, this);
      _nCyc++;
   }

   public void paint (Graphics g)   {update (g);}

   public void mouseDragged  (MouseEvent mouseevent)  {}
   public void mouseClicked  (MouseEvent mouseevent)  {}
   public void mouseEntered  (MouseEvent mouseevent)  {}
   public void mouseExited   (MouseEvent mouseevent)  {}
   public void mousePressed  (MouseEvent mouseevent)  {}
   public void mouseReleased (MouseEvent mouseevent)  {}
   public void mouseMoved    (MouseEvent mouseevent)  {}

   public void init ()
   {  _w = getWidth ();   _h = getHeight ();   _wh = _w * _h;
      _cX = _w / 2;   _cY = _h / 2;
      _part = new particle [_nPart];
      _pxl  = new int [_wh];
      _dcm  = new DirectColorModel  (24, 0xFF0000, 0xFF00, 0xFF);
      _mis  = new MemoryImageSource (_w, _h, _dcm, _pxl, 0, _w);
      _mis.setAnimated (true);     _mis.setFullBufferUpdates (false);
      _img = createImage (_mis);   _bgCol = 0xFFFFFF;
      for (int i = 0; i < _nPart; i++)
         _part [i] = new particle (0xFFFFFF, i / _w / 2, i % (_h * 5),
                                   0.0D, 0.0D);
      for (int j = 0; j < _wh; j++)  _pxl [j] = _bgCol;
      _sprCol = _bgCol;
      addMouseListener (this);   addMouseMotionListener (this);
   }

   public esite ()
   {  _nPart = 200;  _nCyc = 0;  _rV = 0;  _gV = 0;  _thr = null;  }
}