After posting unable to get to comments section

Following a tutorial on thinkster on building a simple page where you can post titles and links and comment on your posts.

After clicking post my title is posted with a comments link. However when I click on the comments link nothing happens.

Here is my index.html:

<html>
<head>
  <title>Flapper News</title>
  <link href="http://maxcdn.bootstrapcdn.com/bootstrap/3.2.0/css/bootstrap.min.css" rel="stylesheet">
  https://ajax.googleapis.com/ajax/libs/angularjs/1.5.7/angular.min.js
  http://cdnjs.cloudflare.com/ajax/libs/angular-ui-router/0.3.2/angular-ui-router.js
  http://app.js
  <style> .glyphicon-thumbs-up { cursor:pointer } </style>
</head>
<body ng-app="flapperNews">
  
</div>
{{post.upvotes}} {{post.title}} {{post.title}} Comments

Add a new post

{{comment.upvotes}} - by {{comment.author}} {{comment.body}}

Add a new comment

</body> </html>

And here is my app.js page:

var app = angular.module('flapperNews', ['ui.router']); 

app.config([
'$stateProvider',
'$urlRouterProvider',
function($stateProvider, $urlRouterProvider) {

  $stateProvider
    .state('home', {
      url: '/home',
      templateUrl: '/home.html',
      controller: 'MainCtrl'
    })

    .state('posts',{
      url: '/posts{id}',
      templateUrl: '/posts.html',
      controller: 'PostsCtrl'
    });

  $urlRouterProvider.otherwise('home');
}])

app.factory('posts', [function(){
  var o = {
    posts:[]
  };
  return o;
}])

app.controller('MainCtrl', [    
'$scope',
'posts',
function($scope, posts){
  $scope.test = 'Hello world!';

  $scope.posts = posts.posts;

 $scope.addPost = function(){
  if(!$scope.title || $scope.title === '') { return; }
  $scope.posts.push({
    title: $scope.title, 
    link: $scope.link,
    upvotes: 0,
    comments: [
    {author: 'Joe', body: 'Cool post!', upvotes: 0},
    {author: 'Bob', body: 'Great idea but everything is wrong!', upvotes: 0}
    ]
  });
  $scope.title = '';
  $scope.link = '';
 }

 $scope.incrementUpvotes = function(post) {
  post.upvotes += 1;
 }
}])

app.controller('PostsCtrl', [
'$scope',
'$stateParams',
'posts',
function($scope, $stateParams, posts){
  $scope.post = posts.posts[$stateParams.id];

  $scope.addComment = function(){
  if($scope.body === '') { return; }
  $scope.posts.push({
    body: $scope.body,
    author: 'user',
    upvotes: 0
  });
  $scope.body = '';
  }
}]);


Source: stackoverflow-javascript