New Twiddle

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  prop1: Ember.computed(function() {
    return '1) read only prop';
  }).readOnly(),
  prop2: Ember.computed({
    get() {
    	return '2) computed only get';
    }
  }),
  prop3: Ember.computed.oneWay('prop3Val'),
  prop3Val: '3) computed oneWay',
});

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
{{outlet}}
<br>
<br>
{{prop1}}

{{input type='button' value='Change 1' click=(action (mut prop1) 'something else')}} 
<br>
{{prop2}}

{{input type='button' value='Change 2' click=(action (mut prop2) 'something else')}} 
<br>
{{prop3}}

{{input type='button' value='Change 3' click=(action (mut prop3) 'something else')}} 

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"
  }
}