Which game is credited with pioneering the first successful in-game microtransaction store for a major PC title, establishing the now-common 'games as a service' retail model?

The gaming industry has transformed how digital products are sold with innovative retail strategies within virtual worlds. From cosmetic items to expansion packs, in-game purchasing has evolved dramatically over the years. This trivia question explores a pivotal moment in gaming retail history that changed how developers monetize their games and how players shop in virtual environments. Test your knowledge of this gaming retail milestone!

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Team Fortress 2 with the Mann Co. Store (2010)
World of Warcraft with the Blizzard Store (2009)
Counter-Strike with the Weapon Case system (2013)
League of Legends with the Riot Store (2011)