2 min lesson
How to use this week
Respond to "What is the single completion exercise you should run on every new feature you learn this week?" Give the answer first and the evidence second.
Step 1 of 3
This week builds the lens first, then loads it with ammunition. Treat the five-layer model as the spine and everything else as muscle hung on it. Every module should resolve back to one question: where does this make good changes easier to produce or evidence cheaper to generate, without disturbing Layer 5?
Interactive diagram. Tab through its regions; each focused region shows its detail in the panel below.
diagram: lens-test
Two questions decide whether a feature is something to lead with or a constraint to flag: which half of the job it serves and whether it leaves layer 5 intact.