New Twiddle

components.my-component\.js

import Component from '@glimmer/component';
import { action } from '@ember/object';
import { tracked } from '@glimmer/tracking';

export default class extends Component {
  @tracked fuck;
  @tracked childFuck;
  
  constructor(){
    super(...arguments);
    this.fuck = 'you';
  }
  
  get fuckNotEqualToChildFuck(){
    return this.fuck != this.childFuck;
  };
  
  @action
  updateChildFuck(){
    console.log('update child fuck')
  	this.childFuck = event.target.value;
  }
  
  @action
  updateFuck(){
    console.log('update fuck')
  	this.fuck = event.target.value;
  }
}

components.my-sub-component\.js

import Component from '@glimmer/component';
import { action } from '@ember/object';
import { tracked } from '@glimmer/tracking';

export default class extends Component {
  @tracked _fuck;
  
  get processedFuck(){
    this._fuck = this.args.fuck;
  	return `Fuck ${this.args.fuck}`;
  }
}

controllers.application\.js

import Controller from '@ember/controller';

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

templates.application\.hbs

<MyComponent/>

templates.components.my-component\.hbs

Parent component 
<br>
Fuck <input value={{this.fuck}} type="input" {{on 'input' updateFuck}} />
Value: {{this.fuck}} 
{{#if this.fuckNotEqualToChildFuck}}
	<br><br><br>
  <div style="color:red">
  	The parent fuck is different than the child fuck.  [parent fuck: {{this.fuck}} / child fuck: {{this.childFuck}}]
  </div>
{{/if}}

<br><br><br>
<MySubComponent @fuck={{this.fuck}} @updateChildFuck={{this.updateChildFuck}}/>

templates.components.my-sub-component\.hbs

<div>
	Sub component 
  <br><br>
  raw value from parent: "{{@fuck}}"
  <br><br>
  Processed fuck: "{{this.processedFuck}}"
  <br><br>
  _fuck: "{{this._fuck}}"
  <input value={{this._fuck}} type="input" {{on 'input' @updateChildFuck}} />
</div>

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": {
  "@ember/render-modifiers": "1.0.2",
    "@glimmer/component": "1.0.0"
  }
}