recomputed on set

controllers.application\.js

import Controller from '@ember/controller';
import { action, computed } from '@ember/object';

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

  variable1 = 0;
  _variable2 = 0;

  @computed('variable1')
  get variable2() {
     return this.variable1 + this._variable2;
  }

  set variable2(value) {
     this._variable2 = value;
  }

  @action
  onClick1() {
     this.set('variable1', this.variable1 + 1);
  }

  @action
  onClick2() {
     this.variable2 = this.variable2 + 1;
  }
}

templates.application\.hbs

<h1>Welcome to {{this.appName}}</h1>
  <br>
  <div>variable1: {{this.variable1}}</div>
  <div>variable2: {{this.variable2}}</div>
  <button {{on "click" this.onClick1}}>change var1</button>
  <button {{on "click" this.onClick2}}>change var2</button>
  <br>
  {{outlet}}
  <br>
<br>

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"
  }
}