This is really similar to the "getting started" feature in our product, Handcraft.com. It's a HTML prototyping tool so you have to write code, but we're aiming it at interaction designers so we've taken care to address the fact that some designers aren't too familiar with writing HTML to do prototyping.
We ended up initially putting you into an introductory prototype when you first start an account where we bring you up to speed on what our tool can do in terms of writing HTML before we go further and show you more about how our tool is special.
Strangely, after launching in the Chrome Web Store, we started getting a lot of feedback from people who had stumbled into it and were discovering HTML for the first time through our getting started guide. They don't have a clue what "HTML prototyping" or "interaction design" is, but they love learning about "how to make websites" with Handcraft.
Just thought I'd share. Great work with Codecademy! I'll be keeping my eye on it and might start forwarding people over if they get stuck with what we have on offer.