New Twiddle

components.my-component\.js

import Component from '@ember/component';
import { classNameBindings } from '@ember-decorators/component';

@classNameBindings('orientationClasses')
export default class extends Component {
  @computed('placement')
  get orientationClasses() {
    switch (this.placement) {
      case 'top':
        return 'hovercard fade-in-down';
      case 'left':
        return 'hovercard-left fade-in-left';
      case 'right':
        return 'hovercard-right fade-in-right';
      default:
        return 'hovercard-bottom fade-in-up';
    }
  }
}

controllers.application\.js

import Controller from '@ember/controller';

export default class ApplicationController extends Controller {
  appName = 'Ember Twiddle';
}

templates.application\.hbs

<h1>Welcome to {{this.appName}}</h1>
<br>
<br>
{{outlet}}
<br>
<br>

<MyComponent />

templates.components.my-component\.hbs

I am working

{{yield}}

twiddle\.json

{
  "version": "0.17.1",
  "EmberENV": {
    "FEATURES": {},
    "_TEMPLATE_ONLY_GLIMMER_COMPONENTS": false,
    "_APPLICATION_TEMPLATE_WRAPPER": true,
    "_JQUERY_INTEGRATION": true
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.5.1/jquery.js",
    "ember": "3.18.1",
    "ember-template-compiler": "3.18.1",
    "ember-testing": "3.18.1"
  },
  "addons": {
    "@glimmer/component": "1.0.0",
    "ember-decorators": "^6.1.1"
  }
}