New Twiddle

components.my-component.js

import Ember from 'ember';

export default Ember.Component.extend({
});

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  
  actions: {
    theSomething(selected) {
      this.set('controllerSelected', selected)
    }
  }
});

helpers.not.js

import Ember from 'ember';

export function not(params/*, hash*/) {
  return !params[0];
}

export default Ember.Helper.helper(not);

styles.app.css

body {
  margin: 12px 16px;
  font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif;
  font-size: 12pt;
}

.target {
  width: 200px;
  height: 200px;
  background-color: red;
}

.target.selected {
  background-color: blue;
}

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
{{my-component selected=controllerSelected doSomething=(action 'theSomething')}}
<br>
<br>

templates.components.my-component.hbs

<div 
  class='target {{if selected 'selected'}}'
  onclick={{action (action doSomething (not selected))}}
/>

twiddle.json

{
  "version": "0.7.1",
  "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"
  }
}