msie = navigator.appVersion.indexOf("MSIE") != -1;

ns4  = !msie && document.layers;



function layerSupport() {

    return document.all || document.layers || document.getElementById;

}



layers = new Array();

layerX = new Array();

layerY = new Array();

cursorX = 0;

cursorY = 0;



function getViewWidth() {

  if (!ns4)

    return document.body.clientWidth;

  else

    return window.innerWidth;

}



function getViewHeight() {

  if (!ns4)

    return document.body.clientHeight;

  else

    return window.innerHeight;

}



function getViewXOffset() {

  if (msie)

    return document.body.scrollLeft;

  else

    return window.pageXOffset;

}



function getViewYOffset() {

  if (msie)

    return document.body.scrollTop;

  else

    return window.pageYOffset;

}



function getLayerX(i) {

    return layerX[i];

}



function getLayerY(i) {

    return layerY[i];

}



function moveLayer(i, x, y) {

  layerX[i] = x;

  layerY[i] = y;

  if (msie) {

    layers[i].style.pixelLeft = x;

    layers[i].style.pixelTop = y;

  }

  else if (ns4) {

    layers[i].left = x;

    layers[i].top = y;

  }

  else {

    layers[i].style.left = x + "px";

    layers[i].style.top = y + "px";

  }

}





function outOfBounds(config, x, y, w, h) {

  var result = 0;

  

  // note that fudge factor isn't used for bottom

  if (x < getViewXOffset() - config.xFudge)

    result |= 1; // Left

  else if (x + w >= getViewXOffset() + getViewWidth() + config.xFudge)

    result |= 2; // Right

  

  if (y + h >= getViewYOffset() + getViewHeight())

    result |= 4; // Bottom

  else if (y < getViewYOffset() - config.yFudge)

    result |= 8; // Top

    

  return result;

}



function random(bound) {

  return Math.floor(Math.random() * bound);

}



function randomX(config) {

  return getViewXOffset() + random(getViewWidth() - config.imageWidth);

}



function randomY(config) {

  return getViewYOffset() - config.yFudge + random(getViewHeight() + config.yFudge - config.imageHeight);

}



function setVisible(i, show) {

   if (!ns4)

      layers[i].style.visibility = show ? "" : "hidden";

   else

      layers[i].visibility = show ? "show" : "hide";

}



function writeLayer(layercontents, name, x, y) {

    layerX[name] = x;

    layerY[name] = y;

    if (!ns4) {

      document.writeln('<div id="' + name + '" style="position:absolute;left:' + x + ';top:' + y + ';">' + layercontents + '</div>');

      if (msie)

        layers[name] = document.all[name];

      else

        layers[name] = document.getElementById(name);

    }

    else {

      document.writeln('<layer id="' + name + '" left=' + x + ' top=' + y + '>' + layercontents + '</layer>');

      layers[name] = document.layers[name];

    }

}



function writeImage(image, name, x, y) {

    layerX[name] = x;

    layerY[name] = y;

    if (!ns4) {

      document.writeln('<div id="' + name + '" style="position:absolute;left:' + x + ';top:' + y + ';"><img src="' + image + '"></div>');

      if (msie)

        layers[name] = document.all[name];

      else

        layers[name] = document.getElementById(name);

    }

    else {

      document.writeln('<layer id="' + name + '" left=' + x + ' top=' + y + '><img src="' + image + '"></layer>');

      layers[name] = document.layers[name];

    }

}



function writeImages(config) {

  for (var i = 0; i < config.imageCount; i++) {

    var startX = randomX(config);

    var startY = config.startOnScreen ? randomY(config) : -config.imageHeight;

    var name = config.prefix + i;

    writeImage(config.image, name, startX, startY);

  }

}



function cursorXY(e) {

  cursorX = msie ? (getViewXOffset() + event.clientX) : e.pageX;

  cursorY = msie ? (getViewYOffset() + event.clientY) : e.pageY;

}



function captureXY() {

  if (!msie) { document.captureEvents(Event.MOUSEMOVE); }

  document.onmousemove = cursorXY;

}



function config() {

  this.xFudge = 0;

  this.yFudge = 0;

  this.updateInterval = 50;

  this.startOnScreen = true;

  this.imageCount = 1;

}