Depth = luminance stepping, not shadows. Every visible step from canvas to hovered dropdown is a 3% lighter fill on the same hue. No box-shadow, no filter: drop-shadow. The hierarchy is read by the eye, not painted by the renderer.
Borders live at 6–8% white. Three weights only — 0.06, 0.08, 0.10. Anything heavier is a SaaS-template tell; anything lighter disappears on matte displays. The 1px hairlines mark the boundary between luminance steps, they don't create new depth.
The accent is the only saturated color on the page. Every status indicator (success / warn / danger / info) is desaturated to read on dark without screaming. Raw brand green or red would look correct in isolation but pull the eye away from the actual data — and there are 6 metrics above, two of which use the same green delta arrow.
Selected row = TWO signals, not one. Background lift (--bg-4) + 2px left-edge accent rail. The rail is the cheaper signal; the lift is the more expensive one. Together they say "this one row" without needing a checkbox or a hover state to disambiguate.