Navbar weirdness in Codepen

I had a very weird result as to how the navbar layout played out in codepen compared to simply my broswer off of a html file.

The problem in codepen persisted after I boiled down the steps to reproduce to these steps:

Start a new pen
Include boostrap.css, jquery.js and boostrap.js as per the instructions in this video (
paste navbar code from boostrap

Im doing this is Chrome and cleared browser cache
Firefox and Safari gave me same results

Is it codepen or is it me?

Maybe it is the version:

Did the trick, awesome!

Thank you BenGitter!