Rafael Pacalso developed foundational gameplay systems for the pacalso-jjc/2425-2nd-cc3-1b-rpg repository, focusing on the initial implementation of an in-game merchant trading system and a data model for crafting materials. He designed and scaffolded the Merchant class in Java, enabling future stock management and buy/sell transactions, and updated class diagrams and documentation to maintain alignment across the codebase. Additionally, Rafael introduced a Material class with methods to support data-driven crafting rules, emphasizing object-oriented programming principles. His work established a scalable structure for future gameplay features, demonstrating careful attention to documentation and consistency between code and technical diagrams.