The number was later referenced in 1999's System Shock 2, as 45100, and became associated with Looking Glass Studios' identity. In 2015, Warren Spector, who worked on System Shock, and later the Deus Ex games, explained that it was simply the key code to Looking Glass Studios' offices in Cambridge, Massachusetts and that the Fahrenheit 451 connection was just a nice bonus. Many initially believed the number was a reference to Ray Bradbury's novel Fahrenheit 451, but this was later proved to be incorrect. The number 451 was first used in their 1994 game, System Shock, as the code that opened the game's first door.

Looking Glass Studios began experimenting with this genre with 1992's Ultima Underworld: The Stygian Abyss and its success meant it became somewhat of a house style for the developer.

It was among the first to really explore the idea of immersive sims, which are games that give players more freedom and several options for completing the game's objectives, challenging the player to creatively use all the tools at their disposal. Looking Glass Studios was an American game development team who created a handful of games in the 1990s.

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