The glass rule
Glass is for navigation, sheets, and transient overlays — surfaces the user reads through. Cards and content blocks stay opaque (
--surface-elevated+ hairline +--shadow-card).
Apple HIG holds glass to nav and sheets for a reason: glass on content makes blur the dominant texture, and text legibility fights backdrop saturation on every read.
Allowed vs not allowed
Glass — yesTop nav · segmented tabs · modal scrim · sheet card · action library shell · floating menus.
Glass — noCards · tables · form panels · sidebar · banking value cards · equity rows.
Companion rule
Any Matter text that sits over a bloom must be inside glass. Body text fails AA on a saturated bloom without it.
Glass for surfaces you look through. Solid (
--surface-elevated) for surfaces you look at.Don't render a card body in glass for "atmosphere". The blur fights the data.