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',
  
  isBlue: false,
  
  actions: {
    blue() {
      this.toggleProperty('isBlue')
    }
  }
});

styles.app.css

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

.my-component {
  width: 40px;
  height: 40px;
  background-color: red;
}

.my-component.blue {
  background-color: blue;
}

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
{{my-component class=(concat 'my-component ' (if isBlue 'blue'))}}
<br>
{{my-component class='my-component' classNameBindings='isBlue:blue'}}
<button onclick={{action 'blue'}}>Toggle blue</button>
{{outlet}}
<br>
<br>

templates.components.my-component.hbs

{{yield}}

twiddle.json

{
  "version": "0.10.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.6.0",
    "ember-data": "2.6.1",
    "ember-template-compiler": "2.6.0"
  },
  "addons": {}
}