New Twiddle

components.my-header.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',
  isLoggedIn: false,
  actions: {
    toggleLoginState() {
      this.toggleProperty('isLoggedIn');
    }
  }
});

templates.application.hbs

{{my-header showFullHeader=isLoggedIn}}
<h1>Welcome to {{appName}}</h1>
<br>
<br>
{{outlet}}
<button onclick={{action 'toggleLoginState'}}>{{if isLoggedIn "Log Out" "Log In"}}</button>
<br>
<br>

templates.components.my-header.hbs

{{#if showFullHeader}}
FULL HEADER HERE
{{else}}
LOGGED-OUT HEADER
{{/if}}

twiddle.json

{
  "version": "0.9.2",
  "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": "2.6.0",
    "ember-template-compiler": "2.6.0"
  }
}