var nDots = 5;

var Xpos = 155;
var Ypos = 90;


var DELTAT = .01;
var SEGLEN = 9;
var SPRINGK = 10;
var MASS = 0.75;
var GRAVITY = 25;
var RESISTANCE = 15;
var STOPVEL = 0.1;
var STOPACC = 0.1;
var DOTSIZE = 10;
var BOUNCE = 0.75;
var isNetscape = navigator.appName=="Netscape";

var followmouse

//initBalls();

function initBalls()
{

followmouse = getCookie("hvost")
//alert(followmouse)
if (followmouse == null) followmouse = "true"

if (followmouse == "true") {
	for (var i=1; i<nDots; i++) {
	eval("dot" + i + ".style.visibility='visible'");
	}
	
}

 var i = 0;
 dots = new Array();
 for (i = 0; i < nDots; i++) {
 dots[i] = new dot(i);
}


 for (i = 0; i < nDots; i++) {
  dots[i].obj.left = dots[i].X;
  dots[i].obj.top = dots[i].Y;
 }

  setTimeout("startanimate()", 3000);
}


function dot(i) 
{
 this.X = Xpos;
 this.Y = Ypos;
 this.dx = 0;
 this.dy = 0;
 this.obj = eval("dot" + i + ".style");
}


function startanimate() { 
 setInterval("animate()", 20);
}

function setInitPositions() {
	for (i = 0; i < nDots; i++) {
		dots[i].obj.left = Xpos;
  		dots[i].obj.top = Ypos;
 	}
}

/*function setInitPositions()
{
 var startloc = document.all.tags("ball");
 var i = 0;
 for (i = 0; i < startloc.length; i++) {
  dots[i+1].X = startloc[i].offsetLeft +
     startloc[i].offsetParent.offsetLeft;
  dots[i+1].Y = startloc[i].offsetTop +
     startloc[i].offsetParent.offsetTop +
     DOTSIZE/2;
 }
 dots[0].X = dots[1].X;
 dots[0].Y = dots[1].Y - SEGLEN;
}*/
  
//function MoveHandlerIE() {
  //Xpos = window.event.x;
  //Ypos = window.event.y;   
//}

//document.onmousemove = MoveHandlerIE;


function vec(X, Y)
{
 this.X = X;
 this.Y = Y;
}

function springForce(i, j, spring)
{
 var dx = (dots[i].X - dots[j].X);
 var dy = (dots[i].Y - dots[j].Y);
 var len = Math.sqrt(dx*dx + dy*dy);
 if (len > SEGLEN) {
  var springF = SPRINGK * (len - SEGLEN);
  spring.X += (dx / len) * springF;
  spring.Y += (dy / len) * springF;
 }
}


function animate() { 
 if (followmouse == "true") {
 var start = 0;
  dots[0].X = Xpos;
  dots[0].Y = Ypos; 
  start = 1;
 

 for (i = start ; i < nDots; i++ ) {

  var spring = new vec(0, 0);
  if (i > 0) {
   springForce(i-1, i, spring);
  }
  if (i < (nDots - 1)) {
   springForce(i+1, i, spring);
  }

  var resist = new vec(-dots[i].dx * RESISTANCE,
        -dots[i].dy * RESISTANCE);

  var accel = new vec((spring.X + resist.X)/ MASS,
       (spring.Y + resist.Y)/ MASS + GRAVITY);
  
       dots[i].dx += (DELTAT * accel.X);
  dots[i].dy += (DELTAT * accel.Y);
  
  if (Math.abs(dots[i].dx) < STOPVEL &&
      Math.abs(dots[i].dy) < STOPVEL &&
      Math.abs(accel.X) < STOPACC &&
   Math.abs(accel.Y) < STOPACC) {
    dots[i].dx = 0;
    dots[i].dy = 0;
  }

  dots[i].X += dots[i].dx;
  dots[i].Y += dots[i].dy;

  var height, width;
  if (isNetscape) {
      height = window.innerHeight;
      width = window.innerWidth;
  } else { 
	 height = document.body.clientHeight;
      width = document.body.clientWidth;
  }

  if (dots[i].X < 0) {
   if (dots[i].dx < 0) {
    dots[i].dx = BOUNCE * -dots[i].dx;
   }
   dots[i].X = 0;
  }

  dots[i].obj.left = dots[i].X + document.body.scrollLeft;   
  dots[i].obj.top =  dots[i].Y + document.body.scrollTop;  
 }
}
}

function toggleBalls() {
	if (followmouse == "true") {
		for (var i=1; i<nDots; i++) {
		eval("dot" + i + ".style.visibility='hidden'");
	}
		followmouse = "false";
		document.icohvost.src = "/img/ico_hvost_off.gif";
		document.icohvost.alt = "Включить хвост";
		setCookie("hvost","false",getExpDate(30));
		setInitPositions();
		
	} else {
		for (var i=1; i<nDots; i++) {
		eval("dot" + i + ".style.visibility='visible'");
		}
		followmouse = "true";
		document.icohvost.src = "/img/ico_hvost_on1.gif";
		document.icohvost.alt = "Выключить хвост";
		setCookie("hvost","true",getExpDate(30));
		
	}
}