Sierra Entertainment, Inc.[1] is an Worldwide American video game developer and publisher founded in 1979 by Ken and Roberta Williams. Based in Los Angeles, California, the company is currently a subsidiary of Activision Blizzard (a subsidiary of Vivendi SA). Sierra itself owns four in-house development studios: High Moon Studios, Massive Entertainment, Radical Entertainment and Swordfish Studios. Sierra is best known today for its multiple lines of seminal graphic adventure games started in the 1980s (notably King's Quest, Space Quest and Quest for Glory), some of which proved influential in the history of video games. The history of Sierra Entertainment started back in 1979 in the California home of Ken and Roberta Williams. At the time, Ken was working as a contract programmer for IBM, developing an income tax program on a mainframe computer 3,000 miles away from L.A. One night he found a program labeled Adventure on the mainframe. Curious of what it could be, he downloaded it and it turned out to be a copy of Colossal Caves. It was the first true "interactive fiction" computer game and Ken became fascinated with it. Roberta was not very interested in computers at the time, but Ken showed her the game on a terminal he had brought home from work. Roberta, who had been a big fairy tale and adventure fiction lover ever since her childhood, was instantly hooked in this new breed of storytelling and played her way through Colossal Cave with great enthusiasm.