"Thief II" was announced during the Electronic Entertainment Expo on May 13, 1999, as part of a contract between Looking Glass and Eidos Interactive to release four new games in the "Thief" series, beginning with "Thief Gold". The deal had been signed on May 7, roughly three months after "Thief II" entered production. A tech demo of the game, which Bruce Geryk of Games Domain described as "about three rooms with some Mages", was displayed on the show floor. The demo was used to showcase the updated Dark Engine, which featured support for colored lighting, higher polygon models and larger environments. The team revealed their intention to include more levels with human enemies, and announced a projected release date of spring 2000. Plans to include a cooperative multiplayer mode were also detailed at the show. IGN's Jason Bates noted that the "Thief II" display attracted "a bit of a buzz and a small crowd of dedicated onlookers".