Elevation
Depth comes from lines first, shadow second. If it doesn't leave the page, it doesn't get a shadow. In dark mode the ladder flips to a lit top edge, because shadows don't read on near-black.
elev-0
resting · hairline only
elev-1
card
elev-2
card, hovered
elev-3
dropdown
elev-4
modal
elev-5
lightbox, drag
.edge-signal
how "live", "featured" and "current" are marked — an edge, never a fill
.surface-sunken
wells: code blocks, inputs, table headers