Lovely idea of making the reader an active participant! Is this part of a real-world course you are teaching? I'm asking because the one time I got to teach an introduction to programming class to designers I tried writing (almost) all course material in heavily commented source code, encouraging the students to use their IDEs, and this reminded me of that

Yup. I'm teaching a course on Computer Graphics. The idea is that students fork this notebook and start uncommenting the cells to understand what each of them actually does and in what order.