Rows you never declared, and where they come from.
Everything after this step assumes the grid is already on the container — this step is the one line that makes every other rule in the guide make sense.
Grid, from scratch
Six steps, in the order you actually reach for them — no step skippable, none of them long.
The implicit grid explanation finally made this click for me. I had been declaring rows for years without knowing why it sometimes worked anyway.
That is exactly the trap — it works right up until the content count changes. Glad it helped.
Would love a follow-up on subgrid. It is the one part I still avoid.