The public site with existing lessons is here: https://www.oppia.org/library
I'm not sure how socratease.in compares. But Oppia has some cool things like being able to set questions which require more than just multiple choice, e.g. requiring you to put a musical note in the right place on a stave.
I learnt just enough web development to be able to build this. So, it will take me a little bit of time to understand code written by a Google team :)
Congrats! Seriously, this is the best way to learn. We're all on the same journey :)
EDIT: Yes, Oppia doesn't appear to update the URL after each step. So if you refresh the page you're back at the start of the lesson. (They didn't have to do it that way, though: http://www.codemag.com/article/1301091)
just fyi: i was going through the second bitcoin module and hit a broken image link: