This looked like a cool idea.

However, it's clearly insecure so I can't recommend it to anyone.

You say a login is required to run code but I can simply enable the Submit button and everything works? That's just extremely poor design.

The same is true for all of your stuff behind your "paywall." Simply editing the HTML in an editor renders your site usable.

You need to have validation on the server and the client. Simply providing client-side validation is not enough, especially for something that should be considered a teacher or tutorial.