New Twiddle

components.child-item.js

import Ember from 'ember';

export default Ember.Component.extend({
	actions: {
    circleClicked() {
      alert('Circle was clicked!');
      return false;
    }
  }
});

components.parent-item.js

import Ember from 'ember';

export default Ember.Component.extend({
  
  click() {
  	alert('Parent was clicked -- should NOT have happened if the circle was clicked!');
  }
});

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Event Propogation Confusion'
});

styles.app.css

body {
  margin: 12px 16px;
  font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif;
  font-size: 12pt;
}

.parent-item {
  cursor: pointer;
  width: 200px;
  height: 300px;
  background-color: #29b6f6;
}

.child-item {
  width: 70px;
  height: 70px;
}

.child-circle {
  cursor: pointer;
  border-radius: 50%;
  width: 100%;
  height: 100%;
  display: block;
  border: 2px solid black;
  background-color: #ff5722;
}

templates.application.hbs

<br>
<br>
{{parent-item class="parent-item"}}
<br>
<br>

templates.components.child-item.hbs

<div class="child-circle" {{action "circleClicked"}}>
</div>

templates.components.parent-item.hbs

{{child-item class="child-item"}}

twiddle.json

{
  "version": "0.13.0",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.16.2",
    "ember-template-compiler": "2.16.2",
    "ember-testing": "2.16.2"
  },
  "addons": {
    "ember-data": "2.16.3"
  }
}