New Twiddle

components.game-defender.js

import Ember from 'ember';

export default Ember.Component.extend({
  left: 0
});

components.game-enemy.js

import Ember from 'ember';

export default Ember.Component.extend({
});

components.game-field.js

import Ember from 'ember';

export default Ember.Component.extend({
  onMouseOver(e) {
    debugger;
    this.set('cursor',{}); 
  }
});

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle'
});

styles.app.css

body {
  margin: 12px 16px;
  font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif;
  font-size: 12pt;
}
.field {
  background: black;
  width: 300px;
  height: 300px;
  position: relative;
}

.defender {
  position: absolute;
  height: 4px;
  background: blue;
  width: 20px;
  bottom: 0;
}

.enemy {
  position: absolute;
}

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
{{#game-field as |game|}}
  {{game-enemy on-goal=game.fightEnemy}}
  {{game-defender}}
{{/game-field}}
<br>
<br>

templates.components.game-defender.hbs

<div class="defender" style="left:{{left}}px">
</div>

templates.components.game-enemy.hbs

{{yield}}

templates.components.game-field.hbs

<div class="field">

{{yield}}
</div>

tests.helpers.destroy-app.js

import Ember from 'ember';

export default function destroyApp(application) {
  Ember.run(application, 'destroy');
}

tests.helpers.resolver.js

import Resolver from '../../resolver';
import config from '../../config/environment';

const resolver = Resolver.create();

resolver.namespace = {
  modulePrefix: config.modulePrefix,
  podModulePrefix: config.podModulePrefix
};

export default resolver;

tests.helpers.start-app.js

import Ember from 'ember';
import Application from '../../app';
import config from '../../config/environment';

const { run } = Ember;
const assign = Ember.assign || Ember.merge;

export default function startApp(attrs) {
  let application;

  let attributes = assign({rootElement: "#test-root"}, config.APP);
  attributes = assign(attributes, attrs); // use defaults, but you can override;

  run(() => {
    application = Application.create(attributes);
    application.setupForTesting();
    application.injectTestHelpers();
  });

  return application;
}

tests.test-helper.js

import resolver from './helpers/resolver';
import {
  setResolver
} from 'ember-qunit';

setResolver(resolver);

twiddle.json

{
  "version": "0.12.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": true
  },
  "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"
  }
}