Hi, I only checked it out on my phone for a minute so please don't take my comments too serious.
I think I like the idea and you have some slick visuals on there. Unfortunately not really usable on small screens, but that's a comment issue with anything code related. In any case it might be helpful to see it embedded as widgets in documentation to explain code segments which explain how to use a library or framework as an alternative to annotating the code snippets and having explanations in copy below.
While playing around with it my initial issue was that I wasn't sure if it was going to "play" automatically or if I could control when I was ready to skip to the next step / explanation. The auto play really didn't work for me in the sense that it was either to quick or unexpected. I would prefer to control the pace myself, especially if it's about reading code where I might want to stop and ponder. I think I would like to simply click a next button, perhaps shown as an arrow next to the current "box". A back/previous button next to the restart button wouldn't be nice as well. Hopefully that wouldn't complicate the UI to much.
The next issue was related to my small viewport: I missed the pop-ups because it (at least on Chrome for Android) did not automatically scroll to the next one. I would consider that would be very helpful for longer code segments.
Hope this helps. Good luck and good job in any case.
