//JS pseudo TurboPascal simulator script
var isAni=1;

var pi=3.14159265;
var NUMDOTS=900;
var N=20;
var NCol=16;
var Infinity=10000000000.0;
var Epsilon=0.00000000001;
var Delta=0.0001;
var Signum=1.0;
var Str=100;
var V3D=0.66;
var b=0.8;

function Point()
{ this.X=0;
  this.Y=0;
  return(this);
};

var xmin, xmax, ymin, ymax;
var sright, sleft, sbottom, stop;
var P=new Array(N+1);
for (var i=0; i<=N; i++) P[i]=new Point();
var P_old=new Point();
var P_new=new Point();
var Dir=new Point();
var dist=new Array(N+1);
var Norm;
var Col=["#442200","#ffcc88"];

function Init()
{ var ii;
  isAni=0;
  setcolor(15);
  bar(0, 0, 300, 150);
  N=12+4*Math.floor(Math.random()*3);
  SetFrame(0,0,180+20*Math.floor(Math.random()*3),150);
  SetBorder(-b,b,-b,b);
  PointInit();
  P_new.X=0.0;
  P_new.Y=0.0;
  Dir.X=Signum*(1.0-Delta);
  Dir.Y=Delta;
  Norm=Math.sqrt(sqr(Dir.X)+sqr(Dir.Y));
  Dir.X/=Norm;
  Dir.Y/=Norm;
  for (ii=1; ii<=20; ii++) Calculate();
  for (ii=1; ii<20; ii++) Animate(1); Animate();
}

function PointInit()
{ var ii;
  for (ii=0; ii<=N; ii++)
  { P[ii].X=Math.cos(2.0*pi*ii/(N));
    P[ii].Y=Math.sin(2.0*pi*ii/(N));
  }
}

function Calculate()
{ var ii, iiDistMin;
  var pp, qq, DistMin;
  var Dir0=new Point();
  var Dir1=new Point();

  P_old.X=P_new.X;
  P_old.Y=P_new.Y;
  for (ii=1; ii<=N; ii++)
    dist[ii]=Infinity;
  for (ii=1; ii<=N; ii++)
  { pp= (P_old.Y-P[ii-1].Y)*(P[ii].X-P[ii-1].X)-
        (P_old.X-P[ii-1].X)*(P[ii].Y-P[ii-1].Y);
    qq= Dir.X*(P[ii].Y-P[ii-1].Y)-Dir.Y*(P[ii].X-P[ii-1].X);
    if ((Math.abs(pp)>Epsilon)&&(Math.abs(qq)>Epsilon))
      dist[ii]=pp/qq;
  }
  DistMin=Infinity;
  for (ii=1; ii<=N; ii++)
  { if (dist[ii]>Epsilon)
    { if (dist[ii]<DistMin)
      { DistMin=dist[ii];
        iiDistMin=ii;
      }
    }
  }
  if (1.1*DistMin<Infinity)
  { P_new.X=P_old.X+DistMin*Dir.X;
    P_new.Y=P_old.Y+DistMin*Dir.Y;
    Norm=1.0/(sqr(P[iiDistMin].X-P[iiDistMin-1].X)+
              sqr(P[iiDistMin].Y-P[iiDistMin-1].Y));
    Norm*=(Dir.X*(P[iiDistMin].X-P[iiDistMin-1].X)+
           Dir.Y*(P[iiDistMin].Y-P[iiDistMin-1].Y));
    Dir0.X=(P[iiDistMin].X-P[iiDistMin-1].X)*Norm;
    Dir0.Y=(P[iiDistMin].Y-P[iiDistMin-1].Y)*Norm;
    Dir.X*=-1.0;
    Dir.X+=2.0*Dir0.X;
    Dir.Y*=-1.0;
    Dir.Y+=2.0*Dir0.Y;
    Norm=Math.sqrt(sqr(Dir.X)+sqr(Dir.Y));
    Dir.X/=Norm;
    Dir.Y/=Norm;
  }
}

function SetFrame (theLeft, theTop, theRight, theBottom)
{ sleft   = theLeft;
  sright  = theRight;
  stop    = theTop;
  sbottom = theBottom;
}

function SetBorder(theLeftX, theRightX,  theBottomY, theTopY)
{ xmin = theLeftX;
  xmax = theRightX;
  ymin = theBottomY;
  ymax = theTopY;
}  

function ScreenX(theRealX){ return(Math.round((theRealX-xmin)/(xmax-xmin)*(sright-sleft)+sleft)); }  
function ScreenY(theRealY){ return(Math.round((ymax-theRealY)/(ymax-ymin)*(sbottom-stop)+stop)); }  
function sqr(xx) { return(xx*xx); }

function Animate(bb)
{ var ii, jj;
  if ((isAni)||(bb))
  { //setcolor(Math.floor(Math.random()*2)*15);    
    ctx.strokeStyle=Col[Math.floor(Math.random()*2)];
    for (ii=1; ii<=NCol; ii++)
    { Calculate();
      for (jj=-4; jj<=4; jj++)
      { moveto(ScreenX(P_old.X+V3D*jj),ScreenY(P_old.Y));
        lineto(ScreenX(P_new.X+V3D*jj),ScreenY(P_new.Y));
      }
    }
  }  
  if (keypressed())
  { key=readkey();
    if ((key=='n')||(key=='N')) { Init(); return; }
    if ((key=='s')||(key=='S')||(key=='')) { isAni=1-isAni; }
    if ((key=='e')||(key=='E')) 
    { closegraph();
      ctx.canvas.width=640;
      ctx.canvas.height=480;
      ctx.lineWidth=1;
      exit();
      return;
    }
  }
  if(!bb) setTimeout("Animate()",100);
}

function run()
{ if (nreadln<1)
  { writeln('keys: s - start/stop | n - new | e - end');
    write('press Enter to continue ...');
    readln('');
    return;
  }
  if (nreadln<2)
  { initgraph(); 
    ctx.canvas.width=300;
    ctx.canvas.height=150;
    ctx.lineWidth=0.25;
    nreadln++;
    Init();
  }
}