Side gutter for text on phones: 20 px by default, never below 16 px (px-gutter-mobile, .mll-gutter, Band gutter, FeatureShowcase, StickyMobileCTA, SnapCarousel bleed).
--safe-topenv(safe-area-inset-top, 0px)
env(safe-area-inset-top): the notch or status bar. Non-zero only with viewport-fit=cover.
--safe-rightenv(safe-area-inset-right, 0px)
env(safe-area-inset-right): landscape notch side.
--safe-bottomenv(safe-area-inset-bottom, 0px)
env(safe-area-inset-bottom): the iOS home indicator (StickyMobileCTA pads by it).