Within Entertainment Computing, games research has grown to be its own area, with numerous publication venues dedicated to it. As this area evolves, it is fruitful to examine its overall development—which subcommunities and research interests were present from the start, which have come and gone, and which are currently active—to better understand the research community as a whole and where it may proceed. In this paper, we present a data-driven analysis and interactive visualization tool to shed light on how technical domains within the games research field have evolved from 2000 to 2013, based on publication data from over 8000 articles collected from 48 games research venues, including Entertainment Computing, FDG, AIIDE, and DiGRA. The approach we present is descriptive. We first used data mining algorithms to group related papers into clusters of similar research topics and evolve these clusters over time. We then designed an interactive visualization system, named Seagull, comprised of Sankey diagrams that allow us to interactively visualize and examine the transition and coalescing of different clusters across time. We present our descriptive analysis in this paper and also contribute the visualization interface to allow other researchers to examine the data and develop their own analysis.