World of Warcraft
"World of Warcraft" was first announced by Blizzard at the ECTS trade show in September 2001. Released in 2004, development of the game took roughly 4–5 years, including extensive testing. The 3D graphics in "World of Warcraft" use elements of the proprietary graphics engine originally used in "Warcraft III". The game was designed to be an open environment where players are allowed to do what they please. Quests are optional and were designed to help guide players, allow character development, and to spread characters across different zones to try to avoid what developers called "player collision". The game interface allows players to customize appearance and controls, and to install add-ons and other modifications.
Role-playing video game
Among the best-selling PC RPGs overall is the massively multiplayer online game "World of Warcraft" with 11.5 million subscribers as of May 2010. Among single player PC RPGs, "Diablo II" has sold the largest amount, with the most recently cited number being over 4 million copies as of 2001. However, copies of the "Diablo: Battle Chest" continued to be sold in retail stores, with the compilation appearing on the NPD Group's top 10 PC games sales, list as recently as 2010. Further, "Diablo: Battle Chest" was the 19th best selling PC game of 2008—a full seven years after the game's initial release; and 11 million users still played "Diablo II" and "StarCraft" over Battle.net in 2010. As a franchise, the "Diablo" series has sold over 20 million copies, not including "Diablo III" which was released for Windows and OS X in 2012.