Use named tokens; don't invent intermediates. If a layout needs 20px, ask whether it should be 16 or 24 — the answer is almost always one of those.
12 columns, 16px gutters, max-width 1200px, side padding 24–48px. Headlines occupy 5–7 columns; body and rail 4–5 columns. Empty columns earn the layout its breath.
copy column · 5/12
The Signal uses a single 720px column of measure, centered on Paper. Don't apply the 12-col grid there.
1px solid --subtle. The card joins the grid; it doesn't float above it.
Save shadows for elevation that means something — modals, popovers — not for static cards.
The brand is square. Default to 0 or 2px. 4px for in-app inputs and chat bubbles. 8px for the few cards that warrant it. Pill only on tag chips.