Dark-mode card grids where the only chromatic event is a bright blue-to-violet gradient stroke, 1–2px wide, tracing each card's rounded edge — often animating a sweep of light around the perimeter on hover. Surfaces stay flat and shadowless; the border is the entire design.
Primary actionA card whose rounded 1px edge carries a #3b82f6→#8b5cf6 gradient — built with a padded gradient layer and mask-composite: exclude — with a bright highlight that sweeps around the perimeter when hovered.