Hacker

From the cassette inlay:

It's late and you've spent the night working electronic bulletin boards with your computer.
You're ready to quit but decide to call up just one more. Being tired, you accidentally call the wrong number and, before you can hang up, your computer screen turns blue.
The words "Logon please" appear.
What do you do now?
You don't know the password.
You don't even know what computer system you've hacked into.
But you do know you want to find out more.
How? You've found your way in.
Now find your way out.

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Hacker is a 1985 computer game by Activision. It was designed by Steve Cartwright, produced by Brad Fregger and was released for the Amiga, Amstrad CPC, Apple II, Atari XL/XE, Atari ST, Commodore 64, Macintosh, MS-DOS, MSX and ZX Spectrum. The game was released two years after the release of the film WarGames, when computer hacking and computer security were in the limelight.

Source: Wikipedia, "Hacker (video game)", available under the CC-BY-SA License.