New Twiddle

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  list: [
    Ember.Object.create({ on: false, name: 'one' }),
    Ember.Object.create({ on: false, name: 'two' }),
    Ember.Object.create({ on: false, name: 'three' }),
    Ember.Object.create({ on: false, name: 'four' }),
    Ember.Object.create({ on: false, name: 'five' })
  ],
  count: Ember.computed('list.@each.on', {
    get() {
      return this.get('list').filter(i => i.on).length;
    }
  }),
  actions: {
    toggle(item) {
      item.toggleProperty('on')
    }
  }
});

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<ul>
	{{#each list as |item|}}
  	<li>
    	<button style="{{if item.on "color: red"}}" {{action "toggle" item}}>{{item.name}}</button>
    </li>
  {{/each}}
</ul>

<p>Count: {{count}}</p>

twiddle.json

{
  "version": "0.12.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.12.0",
    "ember-template-compiler": "2.12.0",
    "ember-testing": "2.12.0"
  },
  "addons": {
    "ember-data": "2.12.1"
  }
}