With a background image on, glass surfaces used surface-alpha 50% + 10px blur, so the feed read
straight THROUGH the nav/menus/popovers (user-reported: distractingly transparent). Raised to
72%/80%/85% + 14px blur — the backdrop image still shows as soft colour, but content behind no longer
punches through. Verified in-browser: nav bg alpha 0.5 -> 0.72, no inline override on a clean pref.
peter
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