What a lesson holds

A learner opens a lesson with one question: what will I be able to do when I close it. Everything on the page answers that question or it does not belong there.

The six parts

Part	Required	What it is
Title and one-line goal	yes	What the learner can do afterwards, in one sentence
Body	yes	Markdown in English, Korean, Japanese and Simplified Chinese
Runnable sample	yes	A folder in a sample repository, the command that runs it, and the screen it produces
Check	yes	A small task the learner does to confirm they got it
Video or short	no	A YouTube id
Related articles	no	Links to the magazine

The sample is the lesson

A lesson that cannot be run is a description. The sample must build from its own folder against published packages only — no path to someone else's checkout, no unpublished fork. If a reader copies the folder and runs the command, the screen in the lesson appears.

One claim per lesson

Split by what the learner can take away at once, not by how the material is organised. If two ideas need two separate "now try this" moments, they are two lessons.

Crew courses keep the same shape

Crews teaching paid courses keep the same shape. That is what lets a paid course point back to the free path it deepens.