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

public class Logistic extends Applet
{
      Graphics      bG;
      Graphics      sG;
      Image         bI;

      Color         back         = new Color(247, 243, 234);
      Color         cobback      = new Color(192, 255, 192);
      Color         coblines     = new Color(0, 255, 0);
      Color         timeback     = new Color(192, 192, 255);
      Color         timelines    = new Color(0, 0, 255);
      Color         function     = new Color(255, 0, 0);
      Color         diagonal     = new Color(0, 0, 0);
      Color         ameter       = new Color(255, 192, 192);
      Color         black        = new Color(0, 0, 0);

      double        x, y, ox, oy, px, py;
      double        C = 1000;
      double        a = 2.8;
      double        start = 50.0;

      int           n = 40;
      int           ok;
      int           k;

      public void init()
      {
             bI = createImage(this.size().width, this.size().height);
             bG = bI.getGraphics();
             ox = start;
             oy = start;
             ok = 0;
             drawback();
      }

      public void paint(Graphics g)
      {
             g.drawImage(bI, 0, 0, this);
             sG = getGraphics();
      }

      public void update(Graphics g)
      {
             g.drawImage(bI, 0, 0, this);
      }


       public int cyscale(double z)
       {
              int iy;
              iy = (int) java.lang.Math.round(205 - 200 * z / C);
              return iy;
       }

       public int cxscale(double z)
       {
              int ix;
              ix = (int) java.lang.Math.round(5 + 200 * z / C);
              return ix;
       }

       public int txscale(int z)
       {
              int ix;
              ix = (int) (215 + java.lang.Math.round(z * 200.0 / n));
              return ix;
       }

       public int ascale(double z)
       {
              int ix;
              ix = (int) (10 + java.lang.Math.round((a - 2) * 200));
              return ix;
       }

       public void drawback()
       {
              bG.setColor(back);
              bG.fillRect(0, 0, 421, 251);
              bG.setColor(cobback);
              bG.fillRect(5, 5, 201, 201);
              bG.setColor(timeback);
              bG.fillRect(215, 5, 201, 201);
              bG.setColor(coblines);
              for (int iy = 5; iy < 206; iy = iy + 20)
              {
                  bG.drawLine(5, iy, 205, iy);
                  bG.drawLine(iy, 5, iy, 205);
              }
              bG.setColor(timelines);
              for (int iy = 5; iy < 206; iy = iy + 20)
              {
                  bG.drawLine(215, iy, 415, iy);
              }
              for (int iy = 0; iy < n + 1; iy = iy + 10)
              {
                  bG.drawLine(txscale(iy), 5, txscale(iy), 205);
              }

              bG.setColor(diagonal);
              bG.drawLine(5, 205, 205, 5);
              bG.setColor(function);
              px = 0;
              py = 0;
              for (int i = 1; i < 201; i = i + 1)
              {
                   x = px + C / 200.0;
                   y = x * a * (1 - x / C);
                   bG.drawLine(cxscale(px), cyscale(py), cxscale(x), cyscale(y));
                   px = x;
                   py = y;
              }
              bG.setColor(ameter);
              bG.fillRect(10, 215, ascale(a) - 9, 31);
              bG.setColor(black);
              bG.drawLine(10, 215, 10, 245);
              bG.drawLine(210, 215, 210, 245);
              bG.drawLine(410, 215, 410, 245);
              bG.drawLine(10, 230, 410, 230);
              for (int ix = 10; ix < 415; ix = ix + 20)
              {
                  bG.drawLine(ix, 225, ix, 235);
              }
              bG.fillOval(txscale(0) - 2, cyscale(start) - 2, 5, 5);
              bG.fillOval(cxscale(start) - 2, cyscale(0) - 2, 5, 5);
              bG.drawLine(cxscale(start), cyscale(0), cxscale(start), cyscale(start));              
      }

      public boolean mouseDown(Event evt, int mx, int my)
      {
             if  (my < 190)
             {   
                 k = ok + 1;
                 x = a * (1 - ox/C) * ox;
                 y = x;
                 bG.setColor(black);
                 bG.drawLine(cxscale(ox), cyscale(oy), cxscale(ox), cyscale(y));
                 bG.drawLine(cxscale(ox), cyscale(y), cxscale(x), cyscale(y));
                 bG.fillOval(cxscale(ox) - 1, cyscale(y) - 1, 3, 3);
                 if  (k < n + 1)
                 {
                     bG.drawLine(txscale(ok), cyscale(oy), txscale(k), cyscale(y));
                     bG.fillOval(txscale(k) - 1, cyscale(y) - 1, 3, 3);
                 }
                 ok = k;
                 ox = x;
                 oy = y;
            } 
            if  (my > 215)
            {
                 mx = java.lang.Math.max(mx, 10);
                 mx = java.lang.Math.min(mx, 410);
                 a = 2.0 + (mx - 10.0)/200.0;
                 ox = start;
                 oy = start;
                 ok = 0;
                 drawback();
            }
            if (java.lang.Math.abs(my - cyscale(0)) < 10)
            {
                 mx = java.lang.Math.max(mx, 5);
                 mx = java.lang.Math.min(mx, 205);
                 start = C * (mx - 5.0)/200.0;
                 ox = start;
                 oy = start;
                 ok = 0;
                 drawback();
            }
            sG.drawImage(bI, 0, 0, this);
            return true;  
      }

}