var nDots = 2;
var Xpos = 0;
var Ypos = 0;
var DELTAT = .1;
var SEGLEN = 1;
var SPRINGK = 5;
var MASS = 1;
var GRAVITY = 50;
var RESISTANCE = 10;
var STOPVEL = 1;
var STOPACC = 1;
var DOTSIZE = 20;
var BOUNCE = 0.75;
var isNetscape = navigator.appName=="Netscape";
var followmouse = true;


init();

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

	setInitPositions()

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

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



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


function startanimator() 
{	
	setInterval("animator()", 20);
}



function setInitPositions()
{
	var startloc = document.all.tags("LI");
	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 MoveHandler(e)
{
	Xpos = e.pageX;
	Ypos = e.pageY;	  
	return true;
}

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 animator() 
	{	
	var start = 0;
	if (followmouse) {
		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;
		    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;			
		dots[i].obj.top =  dots[i].Y;		
	}
}