Swap :root custom properties under prefers-color-scheme: dark or a data-theme attribute—utilities read tokens, not hard-coded hex in every class.
Going deeper
In production utility-first CSS work, Dark surface tokens matters when documents, stylesheets, or apps must stay maintainable across teams and releases—not only in isolated demos.
Common pitfalls
Watch for copy-paste configs, skipping validation or tests, and mixing concerns (structure vs presentation vs behavior) in one layer.
Practice
- Apply one technique from this lesson in the playground.
- Write one interview-style sentence explaining when you would use dark surface tokens on a real project.