I've just released the fully documented source code for The Sentinel as an easy-to-browse website.
It's a lot more fun to explore than the GitHub repository, with cross-references, popups, indexes, statistics and more. I hope you like it!
The next step is to add a whole load of deep dives explaining how Geoff Crammond's proto-VR masterpiece works under the hood, with links into the code itself.
This part will take some weeks as there's a lot to explain, but I'll try to publish them as I go.
Watch this space...