Looking Glass Studios began designing "Thief II" in January 1999. The team's goal was to build on the foundation of "Thief: The Dark Project", a game that "Thief II" project director Steve Pearsall later said was an experiment. He explained that the team had played it safe by including certain "exploration ... or adventure oriented" missions with "jumping and climbing puzzles" in "Thief", and that the new game was significantly more focused on stealth. Combat was given less prominence than in the original. Based on feedback from players and reviewers of "Thief", the team decided to scale back the use of maze-like levels and monsters such as zombies in favor of urban environments and human enemies. Pearsall stated that "Thief"s monsters were negatively received because, unlike the game's human enemies, they did not clearly indicate when they noticed the player. The team sought to remedy this problem by improving the audio cues given by non-human enemies in the sequel.