How to use paper button

[paalss]

Description

I want to start using webcomponents.org, but I fail to even render something so simple as the @polymer/paper-button component. I've followed the instructions in the docs and have no idea what I'm missing.

Expected outcome

I'm expecting the paper button element (which I've provided a raised-prop to) to look like the raised button variant in the demo:

Actual outcome

The paper button isn't rendering. The custom element tag is ignored and my html-page just spits out its children text.

Errors in console

• In Firefox:

  Uncaught TypeError: The specifier “@polymer/iron-flex-layout/iron-flex-layout.js” was a bare specifier, but was not remapped to anything. Relative module specifiers must start with “./”, “../” or “/”.
  

  The Components object is deprecated. It will soon be removed.
  

• In Chrome:

  Uncaught TypeError: Failed to resolve module specifier "@polymer/iron-flex-layout/iron-flex-layout.js". Relative references must start with either "/", "./", or "../".
  

Live Demo

https://github.com/paalss/webcomponents-demo

Steps to reproduce

1. Clone the webcomponents-demo repository
2. Run npm i in it
3. Open the index.html in a browser

Browsers Affected

• Chrome
• Firefox
• Safari 9
• Safari 8
• Safari 7
• Edge
• IE 11
• IE 10