Provides reference and patterns for modern CSS features (2024+) including native nesting, container queries, :has(), @layer cascade control, and modern color functions. Use when writing modern stylesheets, replacing preprocessor features, building responsive components, or creating design systems. モダンCSS機能（2024+）のリファレンスとパターン集。ネイティブネスト、コンテナクエリ、:has()、@layer、モダンな色関数を扱う際に使用。