The collectible Enigma Code fragments appear in the game world as red booklets with a black Wolfenstein logo on the cover, followed by the words "GEHEIM - Enigma Codes". Most code fragments are scattered about in the open just up for grabs, though others are located well out of sight, usually requiring the player to traverse a hidden, sometimes dangerous area to reach. Interacting with certain objects in the environment in a correct manner will sometimes yield cleverly-hidden code pieces.