A 2,800-page free Go book that builds a living simulated world, written in 18 days with AI in the loop

The useful part

The first chapter of The World, the big project book, landed on 2026-08-24. As of yesterday it has ten volumes, 105 chapters, and 2,800 pages, built over 18 working days and 212 commits. That pace is only possible because I draft with AI assistance and spend most of my own time on the part I don't trust the model with, which is checking that everything actually works.

How it works

• Volumes 3 through 9 add physics, terrain, water that flows downhill, plants competing for light, creatures whose traits are evolved rather than programmed, and villagers who remember what happened to them...
• There's a tool that re-executes each command quoted in the text and diffs the output against what the chapter says it should be.
• When a later volume changes an API, the earlier chapter fails that check and gets rewritten before anything ships.
• Volume 10 is where I am now, and the full plan is 25 volumes, so call it 40 percent done.
• If I had to point at one decision that mattered more than the rest, it's the replay.

What to take from it

If you can replay a day you can debug a day, and half the later systems only got finished because I could rewind to the tick where something went wrong. The whole thing is free to read at https://zeroseries.dev/zero/the-world/ and stays free.

Details worth keeping

The repo started on 2026-05-25 as a shelf of teaching books.