Most versions of the game had a similar basic format to the initial Commodore 64 and Atari 800 game, which Crane wrote in six weeks. He based it in part on an incomplete game called Car Wars featuring armed automobiles in a city; this led, for example, to the “ghost vacuum” on the Ecto-1, something not present in the film. Activision obtained the license early in the film’s production, and most of the game was finished by the time Crane watched the film. While pleased with the game, Crane later stated that he regretted not being able to include a better victory screen.The last week of development was spent on the opening screen which plays the Ghostbusters theme.The game was later ported to the Spectrum, Amstrad CPC, and MSX.
At a meeting with hackers, Karl gets to know the student David (Fabian Busch). David and Karl are able to hack into the global data network—which is still, at this point, in its early stages—and their belief in social justice propels them into espionage for the KGB. Driven by contacts with a drug dealer—and by increasing KGB pressure to hack successfully into foreign systems—Karl spirals into a cocaine dependency and grows increasingly alienated from David.
In a drug-addled state, Karl begins to sit in front of his computer for days at a time. Perpetually sleepless, he also grows increasingly delusional. When David publicly reveals the espionage activity in which the two men have been engaged, Karl is left alone to face the consequences. Collapse soon follows. Karl is taken to a hospital to deal with his drug addiction and mysteriously dies afterward.