---
title: 'The mental model'
part: 'Part I — First Stitches: the Turtle'
partNumber: 1
order: 1
subtitle: 'Millimetres, headings, and how paths become stitches'
---

_Content coming soon._

<Run>{`// A simple square — one path, four sides
repeat 4 [ fd 20 rt 90 ]`}</Run>

<Checkpoint chapterId="ch-1">Chapter content coming soon.</Checkpoint>