New Twiddle

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  todos: Ember.computed(function() {
    return [];
  }),
  
  actions: {
   add: function() {
     let todos = this.get('todos');
     this.set('todos', [...todos, 'added']);
   }
  }
});

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<button {{action 'add'}}>Add</button>
<ul>
{{#each todos as |todo|}}
  <li>{{todo}}</li>
{{/each}}
</ul>
{{outlet}}
<br>
<br>

twiddle.json

{
  "version": "0.7.0",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "https://cdnjs.cloudflare.com/ajax/libs/ember.js/2.4.3/ember.debug.js",
    "ember-data": "https://cdnjs.cloudflare.com/ajax/libs/ember-data.js/2.4.3/ember-data.js",
    "ember-template-compiler": "https://cdnjs.cloudflare.com/ajax/libs/ember.js/2.4.3/ember-template-compiler.js"
  }
}