New Twiddle

controllers.application.js

import Ember from 'ember';

const { computed } = Ember;

function comp() {
  const args = Array.from(arguments);
  const cb = args.pop();
  const keys = args.slice();

  args.push(function(key) {
    const hash = keys.reduce((accum, key) => {
      accum[key] = this.get(key);
      
      return accum;
    }, {});

    return cb.call(this, key, hash);
  });
  
	return computed.apply(this, args);
}

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  count: 0,
  computedCount: comp('count', (key, { count }) => `There are ${count}`),
  actions: {
    increment() {
      this.incrementProperty('count');
    }
  }
});

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
<button {{action 'increment'}}>+</button>
{{computedCount}}
<br>
<br>

twiddle.json

{
  "version": "0.13.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.16.2",
    "ember-template-compiler": "2.16.2",
    "ember-testing": "2.16.2"
  },
  "addons": {
    "ember-data": "2.16.3"
  }
}