CodePen is a “playground for the front end side of the web”. It’s a great tool to experiment with code and share it with others. You can easily share your “Pens” by embedding them to your WordPress.com site
You can sign up for CodePen and start making Pens here: http://codepen.io
That’s it! The update will preview live in the Visual Editor so you can see what it looks like without having to click Preview Changes.
The final result will look something like this: