That’s the compiled source of a notebook. I know it can look sort of intimidating, especially if you’re also new to D3; it’s not easy to copy and paste the whole thing directly into a different environment. We think the price is worth it, because it’s necessary to make Observable a nice reactive place to code, but it can definitely be frustrating! I once went through and annotated an example of what you get from that download, which might be helpful: An Observable Notebook.