Did you frame it in terms of the problems you solved rather than the game part? While the interviewer may have a bias against games, it could be spun as "I learned a complicated technology to build this game" or "in order to build this game I had to keep refreshes under XXms which required an innovative solution to state handling". Or perhaps "yes it is a game, but I use it to keep my skills sharp. I use the game to push my boundaries and practice good coding skills, and bring those improvements to my day job"