v155 · margin-trim
Multicol columns
This is the case no selector can reach. In a multi-column container the top of every column needs the margin trimmed, and which item lands at the top of column two is decided during layout — after selectors have matched, and it changes when the container resizes.
Items flowing across columns
The rule
| column | first item | gap above it | state |
|---|
Change the column count and the item count: the items that land at the top of a column change with them. That is why :first-child cannot solve this — the selector would have to match a different element after every resize.