New Twiddle

application.controller.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName:'Ember Twiddle',
  checked: true,
  actions: {
    clickCheck() {
      this.toggleProperty("checked");
      debugger
    }
  }
});

application.template.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
{{outlet}}
<br>
<br>
<p>Control</p>
<input type="checkbox" checked={{checked}} onchange={{action "clickCheck"}} />
{{#if checked}}
Checked
{{else}}
Unchecked
{{/if}}

<p>Unclicked checkbox</p>
<input type="checkbox" checked={{checked}} onchange={{action "clickCheck"}} />
{{#if checked}}
Checked
{{else}}
Unchecked
{{/if}}

twiddle.json

{
  "version": "0.4.10",
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "https://cdnjs.cloudflare.com/ajax/libs/ember.js/1.13.9/ember.debug.js",
    "ember-data": "https://cdnjs.cloudflare.com/ajax/libs/ember-data.js/1.13.11/ember-data.js",
    "ember-template-compiler": "https://cdnjs.cloudflare.com/ajax/libs/ember.js/1.13.9/ember-template-compiler.js"
  }
}