checkboxdynamicclass

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  
  ch: false,
  
  outerdivclass : Ember.computed('ch', function(){
    	if(this.get('ch')){
        return 'flip-container-half'; 
      }
      return 'flip-container';
  }),
  
  actions: {
    toggleCh(){
      this.set('ch', !this.get('ch'));
    }
  }
  
});

styles.app.css

.flip-container .front {
    width: 10em;
    height: 20em;
}

.flip-container-half .front {
    width: 10em;
    height: 10em;
}

templates.application.hbs

<input type='checkbox' checked={{ch}} {{action "toggleCh" on="change"}} />
{{outerdivclass}}
{{test-component height=height outerdivclass=outerdivclass }}

templates.components.test-component.hbs

<div class={{outerdivclass}}>
    <div class="flipper">
        <div class="front">
            RED SIDE
        </div>
        <div class="back">
            BLUE SIDE
        </div>
    </div>
</div>

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"
  }
}