Adventure Game Interpreter

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Adventure Game Interpreter, often shortened to AGI, is the name of a graphical adventure game engine developed by Sierra On-Line. It was initially designed to run the game King's Quest on the PCjr, but was later expanded to play 14 games and several demos, across 8 different platforms including the Amiga, Apple II, Apple IIgs, Atari ST, Macintosh, MS-DOS, and TRS-80 Color Computer. The engine was written in assembler, but it allowed game designers to write scripts in a custom C-like language called Game Adaptation Language, which was compiled into a bytecode that would be interpreted by the engine. As computer hardware continued to improve, Sierra eventually replaced AGI with the Sierra's Creative Interpreter in 1988. Sprites were stored as bitmaps, but background art was stored in a vector format and drawn and painted to the screen.

The first game I played which used AGI was Space Quest II: Vohaul's Revenge, but I have since played the majority of the games which used it.


Game PCjr MS-DOS Apple II Atari ST Amiga Apple IIgs Macintosh TRS-80 CoCo
King's Quest 1984 1987 1984 1986 1987 1987 1987
King's Quest II: Romancing the Throne 1985 1987 1985 1985 1987 1987
The Black Cauldron 1986 1986 1986 1987 1987
Donald Duck's Playground 1986 1986 1986 1986
King's Quest III: To Heir Is Human 1986 1988 1986 1986 1988 1988
Space Quest I: The Sarien Encounter 1986 1986 1986 1987 1987 1987 1986
Leisure Suit Larry In the Land of the Lounge Lizards 1987 1987 1987 1987 1987 1988 1988
Mixed-Up Mother Goose 1987 1990 1987 1988 1988
Police Quest: In Pursuit of the Death Angel 1987 1987 1987 1987 1987 1987
Space Quest II: Vohaul's Revenge 1987 1987 1987 1988 1988 1988
Gold Rush! 1988 1988 1989 1989 1989 1989
Manhunter: New York 1988 1988 1988 1988 1988
King's Quest IV: The Perils of Rosella 1988 1990 1990 1990 1989
Manhunter 2: San Francisco 1989 1990 1990 1989

Additional software: Sierra Christmas Card (1986), Space Quest Demo, Space Quest II Demo, AGI Demo Packs 1-5, King's Quest Demo, King's Quest II Demo, King's Quest III Demo, King's Quest IV Demo, Leisure Suit Larry Demo, Manhunter: New York Demo, Mixed-up Mother Goose Demo, Police Quest Demo, and more.


This is a list of AGI editors that allow you to modify AGI games or create new ones from scratch.


For IBM compatible PCs, AGI supports IBM monochrome, Hercules Graphics Card, Color Graphics Adapter in both RGB and composite modes, PCjr and Tandy Graphics Adapter, and Enhanced Graphics Adapter.



  • The scripting system was really impressive for a game from 1984.
  • By using a scripting system, and letting the engine handle all the nuts and bolts of the hardware, games were easily ported to various platforms.
  • The engine even had a custom music format which could also be easily ported to new audio hardware.
  • Despite being designed for side-view adventure games, the engine was versatile enough to handle action games like the sand skimmer in Space Quest I: The Sarien Encounter or the map navigation system in Man Hunter: New York.
  • The engine could handle several video displays beyond the default for each system.
  • Utilizing color bleeding in CGA composite mode really made the games look great even with only a CGA card.


  • The engine was built for the PCjr, but is wasn't upgraded to take advantage of the superior hardware on the other platforms to which it was later ported. The Amiga could easily handle 320x200 resolution with 4096 colors, while AGI was limited to 160x200 resolution with 16 colors. Likewise, the Amiga had 4-channel digital audio, while AGI only supported 3 square waves and a noise channel.
  • The native resolution used for background graphics (160x200) results in blocky art work, even for the time.
  • Since all the normal keyboard keys were sent to the text input line, only keys like tab, home, and the function keys were allowed to perform other tasks. This made things a bit unusual for games like The Black Cauldron which have to use function keys to shortcut commands like "look." Had the engine used a single button to pop up a input dialog, all the other keys would be usable.


  • Nothing.