The most practically useful additions are `AccentColor` / `AccentColorText` system color keywords — they let you key interactive element colors to the OS accent without JavaScript, which is genuinely cleaner than any workaround in the previous spec. The `light-dark()` function now accepts image values in addition to colors, so you can swap hero images by color scheme in pure CSS rather than reaching for media queries or JS toggles. Older browsers still need the `prefers-color-scheme` fallback, but the pattern is simpler. Comma-separated `@container` queries let you express fallback support for container query features that aren't yet universal — structurally similar to how selector lists handle cascade fallbacks. The `text-fit` property scales font size to fill the containing box width, which has obvious headline and badge use cases. Cross-browser coverage on `text-fit` is still patchy, so check before shipping.