diff --git a/src/echo.js b/src/echo.js
index da1f062..7577563 100644
--- a/src/echo.js
+++ b/src/echo.js
@@ -1,135 +1,134 @@
-(function (root, factory) {
-  if (typeof define === 'function' && define.amd) {
-    define(function() {
-      return factory(root);
-    });
-  } else if (typeof exports === 'object') {
-    module.exports = factory;
-  } else {
-    root.echo = factory(root);
-  }
-})(this, function (root) {
-
-  'use strict';
-
-  var echo = {};
-
-  var callback = function () {};
-
-  var offset, poll, delay, useDebounce, unload;
-
-  var isHidden = function (element) {
-    return (element.offsetParent === null);
-  };
-  
-  var inView = function (element, view) {
-    if (isHidden(element)) {
-      return false;
-    }
+(function() {
+    'use strict';
 
-    var box = element.getBoundingClientRect();
-    return (box.right >= view.l && box.bottom >= view.t && box.left <= view.r && box.top <= view.b);
-  };
+    var echo = {};
+    var _global = this || (0,eval)('this');
+    var root = {};
 
-  var debounceOrThrottle = function () {
-    if(!useDebounce && !!poll) {
-      return;
-    }
-    clearTimeout(poll);
-    poll = setTimeout(function(){
-      echo.render();
-      poll = null;
-    }, delay);
-  };
-
-  echo.init = function (opts) {
-    opts = opts || {};
-    root = opts.viewport || this || (0,eval)('this');
-    var offsetAll = opts.offset || 0;
-    var offsetVertical = opts.offsetVertical || offsetAll;
-    var offsetHorizontal = opts.offsetHorizontal || offsetAll;
-    var optionToInt = function (opt, fallback) {
-      return parseInt(opt || fallback, 10);
-    };
-    offset = {
-      t: optionToInt(opts.offsetTop, offsetVertical),
-      b: optionToInt(opts.offsetBottom, offsetVertical),
-      l: optionToInt(opts.offsetLeft, offsetHorizontal),
-      r: optionToInt(opts.offsetRight, offsetHorizontal)
+    var callback = function () {
     };
-    delay = optionToInt(opts.throttle, 250);
-    useDebounce = opts.debounce !== false;
-    unload = !!opts.unload;
-    callback = opts.callback || callback;
-    echo.render();
-    if (document.addEventListener) {
-      root.addEventListener('scroll', debounceOrThrottle, false);
-      root.addEventListener('load', debounceOrThrottle, false);
-    } else {
-      root.attachEvent('onscroll', debounceOrThrottle);
-      root.attachEvent('onload', debounceOrThrottle);
-    }
-  };
-
-  echo.render = function () {
-    var nodes = document.querySelectorAll('img[data-echo], [data-echo-background]');
-    var length = nodes.length;
-    var src, elem;
-    var view = {
-      l: 0 - offset.l,
-      t: 0 - offset.t,
-      b: (root.innerHeight || document.documentElement.clientHeight) + offset.b,
-      r: (root.innerWidth || document.documentElement.clientWidth) + offset.r
+
+    var offset, poll, delay, useDebounce, unload;
+
+    var isHidden = function (element) {
+        return (element.offsetParent === null);
     };
-    for (var i = 0; i < length; i++) {
-      elem = nodes[i];
-      if (inView(elem, view)) {
 
-        if (unload) {
-          elem.setAttribute('data-echo-placeholder', elem.src);
+    var inView = function (element, view) {
+        if (isHidden(element)) {
+            return false;
         }
 
-        if (elem.getAttribute('data-echo-background') !== null) {
-          elem.style.backgroundImage = "url(" + elem.getAttribute('data-echo-background') + ")";
-        }
-        else {
-          elem.src = elem.getAttribute('data-echo');
-        }
+        var box = element.getBoundingClientRect();
+        return (box.right >= view.l && box.bottom >= view.t && box.left <= view.r && box.top <= view.b);
+    };
 
-        if (!unload) {
-          elem.removeAttribute('data-echo');
-          elem.removeAttribute('data-echo-background');
+    var debounceOrThrottle = function () {
+        if (!useDebounce && !!poll) {
+            return;
         }
+        clearTimeout(poll);
+        poll = setTimeout(function () {
+            echo.render();
+            poll = null;
+        }, delay);
+    };
 
-        callback(elem, 'load');
-      }
-      else if (unload && !!(src = elem.getAttribute('data-echo-placeholder'))) {
+    echo.init = function (opts) {
+        opts = opts || {};
+        root = opts.viewport || _global;
+        var offsetAll = opts.offset || 0;
+        var offsetVertical = opts.offsetVertical || offsetAll;
+        var offsetHorizontal = opts.offsetHorizontal || offsetAll;
+        var optionToInt = function (opt, fallback) {
+            return parseInt(opt || fallback, 10);
+        };
+        offset = {
+            t: optionToInt(opts.offsetTop, offsetVertical),
+            b: optionToInt(opts.offsetBottom, offsetVertical),
+            l: optionToInt(opts.offsetLeft, offsetHorizontal),
+            r: optionToInt(opts.offsetRight, offsetHorizontal)
+        };
+        delay = optionToInt(opts.throttle, 250);
+        useDebounce = opts.debounce !== false;
+        unload = !!opts.unload;
+        callback = opts.callback || callback;
+        echo.render();
+        if (document.addEventListener) {
+            root.addEventListener('scroll', debounceOrThrottle, false);
+            root.addEventListener('load', debounceOrThrottle, false);
+        } else {
+            root.attachEvent('onscroll', debounceOrThrottle);
+            root.attachEvent('onload', debounceOrThrottle);
+        }
+    };
 
-        if (elem.getAttribute('data-echo-background') !== null) {
-          elem.style.backgroundImage = "url(" + src + ")";
+    echo.render = function () {
+        var nodes = document.querySelectorAll('img[data-echo], [data-echo-background]');
+        var length = nodes.length;
+        var src, elem;
+        var view = {
+            l: 0 - offset.l,
+            t: 0 - offset.t,
+            b: (root.innerHeight || root.clientHeight) + offset.b,
+            r: (root.innerWidth || root.clientWidth) + offset.r
+        };
+        for (var i = 0; i < length; i++) {
+            elem = nodes[i];
+            if (inView(elem, view)) {
+
+                if (unload) {
+                    elem.setAttribute('data-echo-placeholder', elem.src);
+                }
+
+                if (elem.getAttribute('data-echo-background') !== null) {
+                    elem.style.backgroundImage = "url(" + elem.getAttribute('data-echo-background') + ")";
+                }
+                else {
+                    elem.src = elem.getAttribute('data-echo');
+                }
+
+                if (!unload) {
+                    elem.removeAttribute('data-echo');
+                    elem.removeAttribute('data-echo-background');
+                }
+
+                callback(elem, 'load');
+            }
+            else if (unload && !!(src = elem.getAttribute('data-echo-placeholder'))) {
+
+                if (elem.getAttribute('data-echo-background') !== null) {
+                    elem.style.backgroundImage = "url(" + src + ")";
+                }
+                else {
+                    elem.src = src;
+                }
+
+                elem.removeAttribute('data-echo-placeholder');
+                callback(elem, 'unload');
+            }
         }
-        else {
-          elem.src = src;
+        if (!length) {
+            echo.detach();
         }
+    };
 
-        elem.removeAttribute('data-echo-placeholder');
-        callback(elem, 'unload');
-      }
-    }
-    if (!length) {
-      echo.detach();
-    }
-  };
+    echo.detach = function () {
+        if (document.removeEventListener) {
+            root.removeEventListener('scroll', debounceOrThrottle);
+        } else {
+            root.detachEvent('onscroll', debounceOrThrottle);
+        }
+        clearTimeout(poll);
+    };
 
-  echo.detach = function () {
-    if (document.removeEventListener) {
-      root.removeEventListener('scroll', debounceOrThrottle);
+    if ((typeof module !== "undefined" && module !== null) && module.exports) {
+        module.exports = echo;
+    } else if (typeof define === 'function') {
+        define(function() {
+            return echo;
+        });
     } else {
-      root.detachEvent('onscroll', debounceOrThrottle);
+        root.echo = echo;
     }
-    clearTimeout(poll);
-  };
-
-  return echo;
-
-});
+}());
\ No newline at end of file