Reagan developed a castling-aware premove feature for the lichess-org/lila repository, focusing on aligning premove behavior with user preferences for rookCastle versus standard castling. Using TypeScript and front end development skills, Reagan updated the king mobility validation to ensure that premoves accurately reflect the chosen castling method, reducing edge-case failures during castling scenarios. This work improved the consistency between the UI and backend by integrating recent chessground fixes, enhancing both game correctness and user trust. The project demonstrated thoughtful cross-repository collaboration and careful dependency management, reflecting a solid understanding of game development principles and maintainable code practices within a complex codebase.