Confused about design of the articles

[jnch009]

I've been going through the lessons (currently starting lesson 3) and it's a lot of fun going through and relearning graphics concepts and coding them up (I'd done a similar course like this in university using Java). The problem I'm trying to get through my head going through these articles is that you claim that each lesson is designed for us to code ourselves. But just reading through the beginning of lesson 3 with rendering a simple scene/y-buffer, there is code showing up as I'm reading the lesson, so how am I supposed to code myself without accidentally exposing myself to code that I shouldn't be using? I think if the code for the lesson was put into a different page entirely and then I could think through the concepts/algorithms and how I'd want to tackle it myself, but yeah I'm just puzzled about how to approach this.