css helper

components.my-component.js

import Ember from 'ember';

export default Ember.Component.extend({
  tagName: ''
});

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  tile: { x: 50, y: 50 }
});

helpers.css.js

import Ember from 'ember';

export function css(_, params) {
  return Ember.String.htmlSafe(
    Object.keys(params).reduce((acc, key) => acc.concat(`${key}: ${addUnitIfNecessary(params[key], key)}`), []).join(';')
  );
}

function addUnitIfNecessary(value, propertyName) {
  if (Ember.$.cssNumber[propertyName]) {
    return value; 
  }
  return isNaN(value) ? value : `${value}px`;
}

export default Ember.Helper.helper(css);

styles.app.css

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

.box {
  position: relative;
  width: 100px;
  height: 100px;
  background: blue;
}

templates.application.hbs

<div>X <input type="range" value={{tile.x}} oninput={{action (mut tile.x) value="target.value"}} min="1" max="100" /></div>
<div>Y <input type="range" value={{tile.y}} oninput={{action (mut tile.y) value="target.value"}} min="1" max="100" /></div>

{{my-component tile=tile}}

templates.components.my-component.hbs

<div class="box" style={{css left=tile.x top=tile.y}}></div>

twiddle.json

{
  "version": "0.12.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.12.0",
    "ember-template-compiler": "2.12.0",
    "ember-testing": "2.12.0"
  },
  "addons": {
    "ember-data": "2.12.1"
  }
}