Socially Relevant Simulation Games (SRSG), a new medium for social interaction, based on real-world skills and skill development, creates a single gaming framework that connects both serious and casual players. Through a detailed case study this paper presents a design process and framework for SRSG, in the context of mixed-reality golf swing simulations. The "World of Golf" SRSG utilizes a real-time expert system to capture, analyze, and evaluate golf swing metrics combining swing data with players' backgrounds, e.g., golf-handicaps, to form individual profiles. Simulation and assessment modules provide the serious player with tools to build golf skills while allowing casual players to engage within a simulated social world. A framework that incorporates simulated golf competitions among these social agents is presented and validated by comparing the usage statistics of 10 PGA Golf Management (PGM) students with 10 non-PGM students.