"

From 2014.igem.org

/**

* Intro.js v0.9.0
* https://github.com/usablica/intro.js
* MIT licensed
*
* Copyright (C) 2013 usabli.ca - A weekend project by Afshin Mehrabani (@afshinmeh)
*/

(function (root, factory) {

 if (typeof exports === 'object') {
   // CommonJS
   factory(exports);
 } else if (typeof define === 'function' && define.amd) {
   // AMD. Register as an anonymous module.
   define(['exports'], factory);
 } else {
   // Browser globals
   factory(root);
 }

} (this, function (exports) {

 //Default config/variables
 var VERSION = '0.9.0';

 /**
  * IntroJs main class
  *
  * @class IntroJs
  */
 function IntroJs(obj) {
   this._targetElement = obj;

   this._options = {
     /* Next button label in tooltip box */
     nextLabel: 'Next →',
     /* Previous button label in tooltip box */
     prevLabel: '← Back',
     /* Skip button label in tooltip box */
     skipLabel: 'Skip',
     /* Done button label in tooltip box */
     doneLabel: 'Done',
     /* Default tooltip box position */
     tooltipPosition: 'bottom',
     /* Next CSS class for tooltip boxes */
     tooltipClass: ,
     /* Close introduction when pressing Escape button? */
     exitOnEsc: true,
     /* Close introduction when clicking on overlay layer? */
     exitOnOverlayClick: true,
     /* Show step numbers in introduction? */
     showStepNumbers: false,
     /* Let user use keyboard to navigate the tour? */
     keyboardNavigation: true,
     /* Show tour control buttons? */
     showButtons: true,
     /* Show tour bullets? */
     showBullets: false,
     /* Scroll to highlighted element? */
     scrollToElement: true,
     /* Set the overlay opacity */
     overlayOpacity: 0.8
   };
 }

 /**
  * Initiate a new introduction/guide from an element in the page
  *
  * @api private
  * @method _introForElement
  * @param {Object} targetElm
  * @returns {Boolean} Success or not?
  */
 function _introForElement(targetElm) {
   var introItems = [],
       self = this;

   if (this._options.steps) {
     //use steps passed programmatically
     var allIntroSteps = [];

     for (var i = 0, stepsLength = this._options.steps.length; i < stepsLength; i++) {
       var currentItem = _cloneObject(this._options.steps[i]);
       //set the step
       currentItem.step = introItems.length + 1;
       //use querySelector function only when developer used CSS selector
       if (typeof(currentItem.element) === 'string') {
         //grab the element with given selector from the page
         currentItem.element = document.querySelector(currentItem.element);
       }

       //intro without element
       if (typeof(currentItem.element) === 'undefined' || currentItem.element == null) {
         var floatingElementQuery = document.querySelector(".introjsFloatingElement");

         if (floatingElementQuery == null) {
           floatingElementQuery = document.createElement('div');
           floatingElementQuery.className = 'introjsFloatingElement';

           document.body.appendChild(floatingElementQuery);
         }

         currentItem.element  = floatingElementQuery;
         currentItem.position = 'floating';
       }

       if (currentItem.element != null) {
         introItems.push(currentItem);
       }
     }

   } else {
      //use steps from data-* annotations
     var allIntroSteps = targetElm.querySelectorAll('*[data-intro]');
     //if there's no element to intro
     if (allIntroSteps.length < 1) {
       return false;
     }

     //first add intro items with data-step
     for (var i = 0, elmsLength = allIntroSteps.length; i < elmsLength; i++) {
       var currentElement = allIntroSteps[i];
       var step = parseInt(currentElement.getAttribute('data-step'), 10);

       if (step > 0) {
         introItems[step - 1] = {
           element: currentElement,
           intro: currentElement.getAttribute('data-intro'),
           step: parseInt(currentElement.getAttribute('data-step'), 10),
           tooltipClass: currentElement.getAttribute('data-tooltipClass'),
           position: currentElement.getAttribute('data-position') || this._options.tooltipPosition
         };
       }
     }

     //next add intro items without data-step
     //todo: we need a cleanup here, two loops are redundant
     var nextStep = 0;
     for (var i = 0, elmsLength = allIntroSteps.length; i < elmsLength; i++) {
       var currentElement = allIntroSteps[i];

       if (currentElement.getAttribute('data-step') == null) {

         while (true) {
           if (typeof introItems[nextStep] == 'undefined') {
             break;
           } else {
             nextStep++;
           }
         }

         introItems[nextStep] = {
           element: currentElement,
           intro: currentElement.getAttribute('data-intro'),
           step: nextStep + 1,
           tooltipClass: currentElement.getAttribute('data-tooltipClass'),
           position: currentElement.getAttribute('data-position') || this._options.tooltipPosition
         };
       }
     }
   }

   //removing undefined/null elements
   var tempIntroItems = [];
   for (var z = 0; z < introItems.length; z++) {
     introItems[z] && tempIntroItems.push(introItems[z]);  // copy non-empty values to the end of the array
   }

   introItems = tempIntroItems;

   //Ok, sort all items with given steps
   introItems.sort(function (a, b) {
     return a.step - b.step;
   });

   //set it to the introJs object
   self._introItems = introItems;

   //add overlay layer to the page
   if(_addOverlayLayer.call(self, targetElm)) {
     //then, start the show
     _nextStep.call(self);

     var skipButton     = targetElm.querySelector('.introjs-skipbutton'),
         nextStepButton = targetElm.querySelector('.introjs-nextbutton');

     self._onKeyDown = function(e) {
       if (e.keyCode === 27 && self._options.exitOnEsc == true) {
         //escape key pressed, exit the intro
         _exitIntro.call(self, targetElm);
         //check if any callback is defined
         if (self._introExitCallback != undefined) {
           self._introExitCallback.call(self);
         }
       } else if(e.keyCode === 37) {
         //left arrow
         _previousStep.call(self);
       } else if (e.keyCode === 39 || e.keyCode === 13) {
         //right arrow or enter
         _nextStep.call(self);
         //prevent default behaviour on hitting Enter, to prevent steps being skipped in some browsers
         if(e.preventDefault) {
           e.preventDefault();
         } else {
           e.returnValue = false;
         }
       }
     };

     self._onResize = function(e) {
       _setHelperLayerPosition.call(self, document.querySelector('.introjs-helperLayer'));
     };

     if (window.addEventListener) {
       if (this._options.keyboardNavigation) {
         window.addEventListener('keydown', self._onKeyDown, true);
       }
       //for window resize
       window.addEventListener("resize", self._onResize, true);
     } else if (document.attachEvent) { //IE
       if (this._options.keyboardNavigation) {
         document.attachEvent('onkeydown', self._onKeyDown);
       }
       //for window resize
       document.attachEvent("onresize", self._onResize);
     }
   }
   return false;
 }

/*
  * makes a copy of the object
  * @api private
  * @method _cloneObject
 */
 function _cloneObject(object) {
     if (object == null || typeof (object) != 'object' || typeof (object.nodeType) != 'undefined') {
         return object;
     }
     var temp = {};
     for (var key in object) {
         temp[key] = _cloneObject(object[key]);
     }
     return temp;
 }
 /**
  * Go to specific step of introduction
  *
  * @api private
  * @method _goToStep
  */
 function _goToStep(step) {
   //because steps starts with zero
   this._currentStep = step - 2;
   if (typeof (this._introItems) !== 'undefined') {
     _nextStep.call(this);
   }
 }

 /**
  * Go to next step on intro
  *
  * @api private
  * @method _nextStep
  */
 function _nextStep() {
   this._direction = 'forward';

   if (typeof (this._currentStep) === 'undefined') {
     this._currentStep = 0;
   } else {
     ++this._currentStep;
   }

   if ((this._introItems.length) <= this._currentStep) {
     //end of the intro
     //check if any callback is defined
     if (typeof (this._introCompleteCallback) === 'function') {
       this._introCompleteCallback.call(this);
     }
     _exitIntro.call(this, this._targetElement);
     return;
   }

   var nextStep = this._introItems[this._currentStep];
   if (typeof (this._introBeforeChangeCallback) !== 'undefined') {
     this._introBeforeChangeCallback.call(this, nextStep.element);
   }

   _showElement.call(this, nextStep);
 }

 /**
  * Go to previous step on intro
  *
  * @api private
  * @method _nextStep
  */
 function _previousStep() {
   this._direction = 'backward';

   if (this._currentStep === 0) {
     return false;
   }

   var nextStep = this._introItems[--this._currentStep];
   if (typeof (this._introBeforeChangeCallback) !== 'undefined') {
     this._introBeforeChangeCallback.call(this, nextStep.element);
   }

   _showElement.call(this, nextStep);
 }

 /**
  * Exit from intro
  *
  * @api private
  * @method _exitIntro
  * @param {Object} targetElement
  */
 function _exitIntro(targetElement) {
   //remove overlay layer from the page
   var overlayLayer = targetElement.querySelector('.introjs-overlay');

   //return if intro already completed or skipped
   if (overlayLayer == null) {
     return;
   }

   //for fade-out animation
   overlayLayer.style.opacity = 0;
   setTimeout(function () {
     if (overlayLayer.parentNode) {
       overlayLayer.parentNode.removeChild(overlayLayer);
     }
   }, 500);

   //remove all helper layers
   var helperLayer = targetElement.querySelector('.introjs-helperLayer');
   if (helperLayer) {
     helperLayer.parentNode.removeChild(helperLayer);
   }

   //remove intro floating element
   var floatingElement = document.querySelector('.introjsFloatingElement');
   if (floatingElement) {
     floatingElement.parentNode.removeChild(floatingElement);
   }

   //remove `introjs-showElement` class from the element
   var showElement = document.querySelector('.introjs-showElement');
   if (showElement) {
     showElement.className = showElement.className.replace(/introjs-[a-zA-Z]+/g, ).replace(/^\s+|\s+$/g, ); // This is a manual trim.
   }

   //remove `introjs-fixParent` class from the elements
   var fixParents = document.querySelectorAll('.introjs-fixParent');
   if (fixParents && fixParents.length > 0) {
     for (var i = fixParents.length - 1; i >= 0; i--) {
       fixParents[i].className = fixParents[i].className.replace(/introjs-fixParent/g, ).replace(/^\s+|\s+$/g, );
     };
   }

   //clean listeners
   if (window.removeEventListener) {
     window.removeEventListener('keydown', this._onKeyDown, true);
   } else if (document.detachEvent) { //IE
     document.detachEvent('onkeydown', this._onKeyDown);
   }

   //set the step to zero
   this._currentStep = undefined;
 }

 /**
  * Render tooltip box in the page
  *
  * @api private
  * @method _placeTooltip
  * @param {Object} targetElement
  * @param {Object} tooltipLayer
  * @param {Object} arrowLayer
  */
 function _placeTooltip(targetElement, tooltipLayer, arrowLayer, helperNumberLayer) {
   var tooltipCssClass = ,
       currentStepObj,
       tooltipOffset,
       targetElementOffset;

   //reset the old style
   tooltipLayer.style.top        = null;
   tooltipLayer.style.right      = null;
   tooltipLayer.style.bottom     = null;
   tooltipLayer.style.left       = null;
   tooltipLayer.style.marginLeft = null;
   tooltipLayer.style.marginTop  = null;

   arrowLayer.style.display = 'inherit';

   if (typeof(helperNumberLayer) != 'undefined' && helperNumberLayer != null) {
     helperNumberLayer.style.top  = null;
     helperNumberLayer.style.left = null;
   }

   //prevent error when `this._currentStep` is undefined
   if (!this._introItems[this._currentStep]) return;

   //if we have a custom css class for each step
   currentStepObj = this._introItems[this._currentStep];
   if (typeof (currentStepObj.tooltipClass) === 'string') {
     tooltipCssClass = currentStepObj.tooltipClass;
   } else {
     tooltipCssClass = this._options.tooltipClass;
   }

   tooltipLayer.className = ('introjs-tooltip ' + tooltipCssClass).replace(/^\s+|\s+$/g, );

   //custom css class for tooltip boxes
   var tooltipCssClass = this._options.tooltipClass;

   currentTooltipPosition = this._introItems[this._currentStep].position;
   switch (currentTooltipPosition) {
     case 'top':
       tooltipLayer.style.left = '15px';
       tooltipLayer.style.top = '-' + (_getOffset(tooltipLayer).height + 10) + 'px';
       arrowLayer.className = 'introjs-arrow bottom';
       break;
     case 'right':
       tooltipLayer.style.left = (_getOffset(targetElement).width + 20) + 'px';
       arrowLayer.className = 'introjs-arrow left';
       break;
     case 'left':
       if (this._options.showStepNumbers == true) {
         tooltipLayer.style.top = '15px';
       }
       tooltipLayer.style.right = (_getOffset(targetElement).width + 20) + 'px';
       arrowLayer.className = 'introjs-arrow right';
       break;
     case 'floating':
       arrowLayer.style.display = 'none';

       //we have to adjust the top and left of layer manually for intro items without element
       tooltipOffset = _getOffset(tooltipLayer);

       tooltipLayer.style.left   = '50%';
       tooltipLayer.style.top    = '50%';
       tooltipLayer.style.marginLeft = '-' + (tooltipOffset.width / 2)  + 'px';
       tooltipLayer.style.marginTop  = '-' + (tooltipOffset.height / 2) + 'px';

       if (typeof(helperNumberLayer) != 'undefined' && helperNumberLayer != null) {
         helperNumberLayer.style.left = '-' + ((tooltipOffset.width / 2) + 18) + 'px';
         helperNumberLayer.style.top  = '-' + ((tooltipOffset.height / 2) + 18) + 'px';
       }

       break;
     case 'bottom-right-aligned':
       arrowLayer.className      = 'introjs-arrow top-right';
       tooltipLayer.style.right  = '0px';
       tooltipLayer.style.bottom = '-' + (_getOffset(tooltipLayer).height + 10) + 'px';
       break;
     case 'bottom-middle-aligned':
       targetElementOffset = _getOffset(targetElement);
       tooltipOffset       = _getOffset(tooltipLayer);

       arrowLayer.className      = 'introjs-arrow top-middle';
       tooltipLayer.style.left   = (targetElementOffset.width / 2 - tooltipOffset.width / 2) + 'px';
       tooltipLayer.style.bottom = '-' + (tooltipOffset.height + 10) + 'px';
       break;
     case 'bottom-left-aligned':
     // Bottom-left-aligned is the same as the default bottom
     case 'bottom':
     // Bottom going to follow the default behavior
     default:
       tooltipLayer.style.bottom = '-' + (_getOffset(tooltipLayer).height + 10) + 'px';
       arrowLayer.className = 'introjs-arrow top';
       break;
   }
 }

 /**
  * Update the position of the helper layer on the screen
  *
  * @api private
  * @method _setHelperLayerPosition
  * @param {Object} helperLayer
  */
 function _setHelperLayerPosition(helperLayer) {
   if (helperLayer) {
     //prevent error when `this._currentStep` in undefined
     if (!this._introItems[this._currentStep]) return;

     var currentElement  = this._introItems[this._currentStep],
         elementPosition = _getOffset(currentElement.element),
         widthHeightPadding = 10;

     if (currentElement.position == 'floating') {
       widthHeightPadding = 0;
     }

     //set new position to helper layer
     helperLayer.setAttribute('style', 'width: ' + (elementPosition.width  + widthHeightPadding)  + 'px; ' +
                                       'height:' + (elementPosition.height + widthHeightPadding)  + 'px; ' +
                                       'top:'    + (elementPosition.top    - 5)   + 'px;' +
                                       'left: '  + (elementPosition.left   - 5)   + 'px;');
   }
 }

 /**
  * Show an element on the page
  *
  * @api private
  * @method _showElement
  * @param {Object} targetElement
  */
 function _showElement(targetElement) {

   if (typeof (this._introChangeCallback) !== 'undefined') {
       this._introChangeCallback.call(this, targetElement.element);
   }

   var self = this,
       oldHelperLayer = document.querySelector('.introjs-helperLayer'),
       elementPosition = _getOffset(targetElement.element);

   if (oldHelperLayer != null) {
     var oldHelperNumberLayer = oldHelperLayer.querySelector('.introjs-helperNumberLayer'),
         oldtooltipLayer      = oldHelperLayer.querySelector('.introjs-tooltiptext'),
         oldArrowLayer        = oldHelperLayer.querySelector('.introjs-arrow'),
         oldtooltipContainer  = oldHelperLayer.querySelector('.introjs-tooltip'),
         skipTooltipButton    = oldHelperLayer.querySelector('.introjs-skipbutton'),
         prevTooltipButton    = oldHelperLayer.querySelector('.introjs-prevbutton'),
         nextTooltipButton    = oldHelperLayer.querySelector('.introjs-nextbutton');

     //hide the tooltip
     oldtooltipContainer.style.opacity = 0;

     if (oldHelperNumberLayer != null) {
       var lastIntroItem = this._introItems[(targetElement.step - 2 >= 0 ? targetElement.step - 2 : 0)];

       if (lastIntroItem != null && (this._direction == 'forward' && lastIntroItem.position == 'floating') || (this._direction == 'backward' && targetElement.position == 'floating')) {
         oldHelperNumberLayer.style.opacity = 0;
       }
     }

     //set new position to helper layer
     _setHelperLayerPosition.call(self, oldHelperLayer);

     //remove `introjs-fixParent` class from the elements
     var fixParents = document.querySelectorAll('.introjs-fixParent');
     if (fixParents && fixParents.length > 0) {
       for (var i = fixParents.length - 1; i >= 0; i--) {
         fixParents[i].className = fixParents[i].className.replace(/introjs-fixParent/g, ).replace(/^\s+|\s+$/g, );
       };
     }

     //remove old classes
     var oldShowElement = document.querySelector('.introjs-showElement');
     oldShowElement.className = oldShowElement.className.replace(/introjs-[a-zA-Z]+/g, ).replace(/^\s+|\s+$/g, );
     //we should wait until the CSS3 transition is competed (it's 0.3 sec) to prevent incorrect `height` and `width` calculation
     if (self._lastShowElementTimer) {
       clearTimeout(self._lastShowElementTimer);
     }
     self._lastShowElementTimer = setTimeout(function() {
       //set current step to the label
       if (oldHelperNumberLayer != null) {
         oldHelperNumberLayer.innerHTML = targetElement.step;
       }
       //set current tooltip text
       oldtooltipLayer.innerHTML = targetElement.intro;
       //set the tooltip position
       _placeTooltip.call(self, targetElement.element, oldtooltipContainer, oldArrowLayer, oldHelperNumberLayer);

       //change active bullet
       oldHelperLayer.querySelector('.introjs-bullets li > a.active').className = ;
       oldHelperLayer.querySelector('.introjs-bullets li > a[data-stepnumber="' + targetElement.step + '"]').className = 'active';

       //show the tooltip
       oldtooltipContainer.style.opacity = 1;
       if (oldHelperNumberLayer) oldHelperNumberLayer.style.opacity = 1;
     }, 350);

   } else {
     var helperLayer       = document.createElement('div'),
         arrowLayer        = document.createElement('div'),
         tooltipLayer      = document.createElement('div'),
         tooltipTextLayer  = document.createElement('div'),
         bulletsLayer      = document.createElement('div'),
         buttonsLayer      = document.createElement('div');

     helperLayer.className = 'introjs-helperLayer';

     //set new position to helper layer
     _setHelperLayerPosition.call(self, helperLayer);

     //add helper layer to target element
     this._targetElement.appendChild(helperLayer);

     arrowLayer.className = 'introjs-arrow';

     tooltipTextLayer.className = 'introjs-tooltiptext';
     tooltipTextLayer.innerHTML = targetElement.intro;

     bulletsLayer.className = 'introjs-bullets';

     if (this._options.showBullets === false) {
       bulletsLayer.style.display = 'none';
     }

     var ulContainer = document.createElement('ul');

     for (var i = 0, stepsLength = this._introItems.length; i < stepsLength; i++) {
       var innerLi    = document.createElement('li');
       var anchorLink = document.createElement('a');

       anchorLink.onclick = function() {
         self.goToStep(this.getAttribute('data-stepnumber'));
       };

       if (i === 0) anchorLink.className = "active";

       anchorLink.href = 'javascript:void(0);';
       anchorLink.innerHTML = " ";
       anchorLink.setAttribute('data-stepnumber', this._introItems[i].step);

       innerLi.appendChild(anchorLink);
       ulContainer.appendChild(innerLi);
     }

     bulletsLayer.appendChild(ulContainer);

     buttonsLayer.className = 'introjs-tooltipbuttons';
     if (this._options.showButtons === false) {
       buttonsLayer.style.display = 'none';
     }

     tooltipLayer.className = 'introjs-tooltip';
     tooltipLayer.appendChild(tooltipTextLayer);
     tooltipLayer.appendChild(bulletsLayer);

     //add helper layer number
     if (this._options.showStepNumbers == true) {
       var helperNumberLayer = document.createElement('span');
       helperNumberLayer.className = 'introjs-helperNumberLayer';
       helperNumberLayer.innerHTML = targetElement.step;
       helperLayer.appendChild(helperNumberLayer);
     }
     tooltipLayer.appendChild(arrowLayer);
     helperLayer.appendChild(tooltipLayer);

     //next button
     var nextTooltipButton = document.createElement('a');

     nextTooltipButton.onclick = function() {
       if (self._introItems.length - 1 != self._currentStep) {
         _nextStep.call(self);
       }
     };

     nextTooltipButton.href = 'javascript:void(0);';
     nextTooltipButton.innerHTML = this._options.nextLabel;

     //previous button
     var prevTooltipButton = document.createElement('a');

     prevTooltipButton.onclick = function() {
       if (self._currentStep != 0) {
         _previousStep.call(self);
       }
     };

     prevTooltipButton.href = 'javascript:void(0);';
     prevTooltipButton.innerHTML = this._options.prevLabel;

     //skip button
     var skipTooltipButton = document.createElement('a');
     skipTooltipButton.className = 'introjs-button introjs-skipbutton';
     skipTooltipButton.href = 'javascript:void(0);';
     skipTooltipButton.innerHTML = this._options.skipLabel;

     skipTooltipButton.onclick = function() {
       if (self._introItems.length - 1 == self._currentStep && typeof (self._introCompleteCallback) === 'function') {
         self._introCompleteCallback.call(self);
       }

       if (self._introItems.length - 1 != self._currentStep && typeof (self._introExitCallback) === 'function') {
         self._introExitCallback.call(self);
       }

       _exitIntro.call(self, self._targetElement);
     };

     buttonsLayer.appendChild(skipTooltipButton);

     //in order to prevent displaying next/previous button always
     if (this._introItems.length > 1) {
       buttonsLayer.appendChild(prevTooltipButton);
       buttonsLayer.appendChild(nextTooltipButton);
     }

     tooltipLayer.appendChild(buttonsLayer);

     //set proper position
     _placeTooltip.call(self, targetElement.element, tooltipLayer, arrowLayer, helperNumberLayer);
   }

   if (this._currentStep == 0 && this._introItems.length > 1) {
     prevTooltipButton.className = 'introjs-button introjs-prevbutton introjs-disabled';
     nextTooltipButton.className = 'introjs-button introjs-nextbutton';
     skipTooltipButton.innerHTML = this._options.skipLabel;
   } else if (this._introItems.length - 1 == this._currentStep || this._introItems.length == 1) {
     skipTooltipButton.innerHTML = this._options.doneLabel;
     prevTooltipButton.className = 'introjs-button introjs-prevbutton';
     nextTooltipButton.className = 'introjs-button introjs-nextbutton introjs-disabled';
   } else {
     prevTooltipButton.className = 'introjs-button introjs-prevbutton';
     nextTooltipButton.className = 'introjs-button introjs-nextbutton';
     skipTooltipButton.innerHTML = this._options.skipLabel;
   }

   //Set focus on "next" button, so that hitting Enter always moves you onto the next step
   nextTooltipButton.focus();

   //add target element position style
   targetElement.element.className += ' introjs-showElement';

   var currentElementPosition = _getPropValue(targetElement.element, 'position');
   if (currentElementPosition !== 'absolute' &&
       currentElementPosition !== 'relative') {
     //change to new intro item
     targetElement.element.className += ' introjs-relativePosition';
   }

   var parentElm = targetElement.element.parentNode;
   while (parentElm != null) {
     if (parentElm.tagName.toLowerCase() === 'body') break;

     //fix The Stacking Contenxt problem.
     //More detail: https://developer.mozilla.org/en-US/docs/Web/Guide/CSS/Understanding_z_index/The_stacking_context
     var zIndex = _getPropValue(parentElm, 'z-index');
     var opacity = parseFloat(_getPropValue(parentElm, 'opacity'));
     if (/[0-9]+/.test(zIndex) || opacity < 1) {
       parentElm.className += ' introjs-fixParent';
     }

     parentElm = parentElm.parentNode;
   }

   if (!_elementInViewport(targetElement.element) && this._options.scrollToElement === true) {
     var rect = targetElement.element.getBoundingClientRect(),
       winHeight=_getWinSize().height,
       top = rect.bottom - (rect.bottom - rect.top),
       bottom = rect.bottom - winHeight;

     //Scroll up
     if (top < 0 || targetElement.element.clientHeight > winHeight) {
       window.scrollBy(0, top - 30); // 30px padding from edge to look nice

     //Scroll down
     } else {
       window.scrollBy(0, bottom + 100); // 70px + 30px padding from edge to look nice
     }
   }

   if (typeof (this._introAfterChangeCallback) !== 'undefined') {
       this._introAfterChangeCallback.call(this, targetElement.element);
   }
 }

 /**
  * Get an element CSS property on the page
  * Thanks to JavaScript Kit: http://www.javascriptkit.com/dhtmltutors/dhtmlcascade4.shtml
  *
  * @api private
  * @method _getPropValue
  * @param {Object} element
  * @param {String} propName
  * @returns Element's property value
  */
 function _getPropValue (element, propName) {
   var propValue = ;
   if (element.currentStyle) { //IE
     propValue = element.currentStyle[propName];
   } else if (document.defaultView && document.defaultView.getComputedStyle) { //Others
     propValue = document.defaultView.getComputedStyle(element, null).getPropertyValue(propName);
   }

   //Prevent exception in IE
   if (propValue && propValue.toLowerCase) {
     return propValue.toLowerCase();
   } else {
     return propValue;
   }
 }

 /**
  * Provides a cross-browser way to get the screen dimensions
  * via: http://stackoverflow.com/questions/5864467/internet-explorer-innerheight
  *
  * @api private
  * @method _getWinSize
  * @returns {Object} width and height attributes
  */
 function _getWinSize() {
   if (window.innerWidth != undefined) {
     return { width: window.innerWidth, height: window.innerHeight };
   } else {
     var D = document.documentElement;
     return { width: D.clientWidth, height: D.clientHeight };
   }
 }

 /**
  * Add overlay layer to the page
  * http://stackoverflow.com/questions/123999/how-to-tell-if-a-dom-element-is-visible-in-the-current-viewport
  *
  * @api private
  * @method _elementInViewport
  * @param {Object} el
  */
 function _elementInViewport(el) {
   var rect = el.getBoundingClientRect();

   return (
     rect.top >= 0 &&
     rect.left >= 0 &&
     (rect.bottom+80) <= window.innerHeight && // add 80 to get the text right
     rect.right <= window.innerWidth
   );
 }

 /**
  * Add overlay layer to the page
  *
  * @api private
  * @method _addOverlayLayer
  * @param {Object} targetElm
  */
 function _addOverlayLayer(targetElm) {
   var overlayLayer = document.createElement('div'),
       styleText = ,
       self = this;

   //set css class name
   overlayLayer.className = 'introjs-overlay';

   //check if the target element is body, we should calculate the size of overlay layer in a better way
   if (targetElm.tagName.toLowerCase() === 'body') {
     styleText += 'top: 0;bottom: 0; left: 0;right: 0;position: fixed;';
     overlayLayer.setAttribute('style', styleText);
   } else {
     //set overlay layer position
     var elementPosition = _getOffset(targetElm);
     if (elementPosition) {
       styleText += 'width: ' + elementPosition.width + 'px; height:' + elementPosition.height + 'px; top:' + elementPosition.top + 'px;left: ' + elementPosition.left + 'px;';
       overlayLayer.setAttribute('style', styleText);
     }
   }

   targetElm.appendChild(overlayLayer);

   overlayLayer.onclick = function() {
     if (self._options.exitOnOverlayClick == true) {
       _exitIntro.call(self, targetElm);

       //check if any callback is defined
       if (self._introExitCallback != undefined) {
         self._introExitCallback.call(self);
       }
     }
   };

   setTimeout(function() {
     styleText += 'opacity: ' + self._options.overlayOpacity.toString() + ';';
     overlayLayer.setAttribute('style', styleText);
   }, 10);

   return true;
 }

 /**
  * Get an element position on the page
  * Thanks to `meouw`: http://stackoverflow.com/a/442474/375966
  *
  * @api private
  * @method _getOffset
  * @param {Object} element
  * @returns Element's position info
  */
 function _getOffset(element) {
   var elementPosition = {};

   //set width
   elementPosition.width = element.offsetWidth;

   //set height
   elementPosition.height = element.offsetHeight;

   //calculate element top and left
   var _x = 0;
   var _y = 0;
   while (element && !isNaN(element.offsetLeft) && !isNaN(element.offsetTop)) {
     _x += element.offsetLeft;
     _y += element.offsetTop;
     element = element.offsetParent;
   }
   //set top
   elementPosition.top = _y;
   //set left
   elementPosition.left = _x;

   return elementPosition;
 }

 /**
  * Overwrites obj1's values with obj2's and adds obj2's if non existent in obj1
  * via: http://stackoverflow.com/questions/171251/how-can-i-merge-properties-of-two-javascript-objects-dynamically
  *
  * @param obj1
  * @param obj2
  * @returns obj3 a new object based on obj1 and obj2
  */
 function _mergeOptions(obj1,obj2) {
   var obj3 = {};
   for (var attrname in obj1) { obj3[attrname] = obj1[attrname]; }
   for (var attrname in obj2) { obj3[attrname] = obj2[attrname]; }
   return obj3;
 }

 var introJs = function (targetElm) {
   if (typeof (targetElm) === 'object') {
     //Ok, create a new instance
     return new IntroJs(targetElm);

   } else if (typeof (targetElm) === 'string') {
     //select the target element with query selector
     var targetElement = document.querySelector(targetElm);

     if (targetElement) {
       return new IntroJs(targetElement);
     } else {
       throw new Error('There is no element with given selector.');
     }
   } else {
     return new IntroJs(document.body);
   }
 };

 /**
  * Current IntroJs version
  *
  * @property version
  * @type String
  */
 introJs.version = VERSION;

 //Prototype
 introJs.fn = IntroJs.prototype = {
   clone: function () {
     return new IntroJs(this);
   },
   setOption: function(option, value) {
     this._options[option] = value;
     return this;
   },
   setOptions: function(options) {
     this._options = _mergeOptions(this._options, options);
     return this;
   },
   start: function () {
     _introForElement.call(this, this._targetElement);
     return this;
   },
   goToStep: function(step) {
     _goToStep.call(this, step);
     return this;
   },
   nextStep: function() {
     _nextStep.call(this);
     return this;
   },
   previousStep: function() {
     _previousStep.call(this);
     return this;
   },
   exit: function() {
     _exitIntro.call(this, this._targetElement);
   },
   refresh: function() {
     _setHelperLayerPosition.call(this, document.querySelector('.introjs-helperLayer'));
     return this;
   },
   onbeforechange: function(providedCallback) {
     if (typeof (providedCallback) === 'function') {
       this._introBeforeChangeCallback = providedCallback;
     } else {
       throw new Error('Provided callback for onbeforechange was not a function');
     }
     return this;
   },
   onchange: function(providedCallback) {
     if (typeof (providedCallback) === 'function') {
       this._introChangeCallback = providedCallback;
     } else {
       throw new Error('Provided callback for onchange was not a function.');
     }
     return this;
   },
   onafterchange: function(providedCallback) {
     if (typeof (providedCallback) === 'function') {
       this._introAfterChangeCallback = providedCallback;
     } else {
       throw new Error('Provided callback for onafterchange was not a function');
     }
     return this;
   },
   oncomplete: function(providedCallback) {
     if (typeof (providedCallback) === 'function') {
       this._introCompleteCallback = providedCallback;
     } else {
       throw new Error('Provided callback for oncomplete was not a function.');
     }
     return this;
   },
   onexit: function(providedCallback) {
     if (typeof (providedCallback) === 'function') {
       this._introExitCallback = providedCallback;
     } else {
       throw new Error('Provided callback for onexit was not a function.');
     }
     return this;
   }
 };

 exports.introJs = introJs;
 return introJs;

}));