Added some documenting comments

web/example_app.dart

@@ -7,21 +7,37 @@ import 'dart:html';
 class ExampleApp extends PolymerElement {
   @published String page = '';
 
+  // Triggered by the on-click event on the buttons.
   void updatePage(Event e, var detail, Node node) {
+    // Get the data-name value from the element
     var pg = (node as Element).dataset['name'];
+
+    // pass the data-name value as the location fragment
+    // for the page. This lets route's Router handle passing
+    // it off to the page attribute.
     window.location.hash = pg;
   }
 
+  // Triggered by the on-change event for our observable
+  // variable 'page'. Observe library is nice in which we only
+  // have to create a callback which has the name of the variable
+  // plus 'Changed' tacked onto it. Receives the old value it used
+  // to contain.
   void pageChanged(oldValue) {
+    // This check shouldn't be necessary as the observe library should
+    // handle this for us. But I'm paranoid ;)
     if(page == oldValue) {
       return;
     } else if(page == '') {
 
+      // If page is blank just remove anything in the container.
       var container =  $['container'];
       container.children.clear();
     } else {
       var element = '';
 
+      // Determine which element we should be displaying based on
+      // what was passed to the location fragment.
       switch(page.toLowerCase()) {
         case 'one':
         case '1':
@@ -40,6 +56,7 @@ class ExampleApp extends PolymerElement {
 
   }
 
+  // Take the element we determined needed to be added, create it and add it.
   void _addElement(String elementName) {
     if(elementName == '') throw new ArgumentError('Must provide an element name');
 

web/routes_example.dart

@@ -9,12 +9,18 @@ import 'package:route/client.dart';
 final MyUrl = new UrlPattern(r'/routes_example/web/routes_example.html#(\w+)');
 
 main() {
+  // Create our router and handlers then start listening.
+  // See route package documentation for more details.
   var router = new Router()..addHandler(MyUrl, route_handler)..listen();
 
 }
 
 void route_handler(String path) {
+  // Since we only have one match group, we're only worried about the
+  // first result.
   var page = MyUrl.parse(path)[0];
+
+  // Grab our custom element and assign to the page property.
   var exampleApp = document.query('example-app').xtag;
   exampleApp.page = page;
 }