Mikkel worked on the ferrocene/ferrocene repository, focusing on improving cross-platform path separator handling in the Rust standard library. He consolidated path separator representations into a single per-platform macro, introduced new constants, and made the is_separator function const to support compile-time evaluation. By refactoring to use a local MAIN_SEPARATOR_STR, he reduced unnecessary imports and simplified the dependency surface. His work, rooted in Rust and system programming, enhanced the maintainability and reliability of path handling across platforms. The changes laid a foundation for future platform-specific extensions and improved code clarity, demonstrating thoughtful engineering within a focused, foundational area of the codebase.