Introduction to Agi Player: Sierra Adventure Game Interpreter

See the Introduction to Agi for common information on what Agi games are and the technology behind them.

Sierra developed interpreters for many different computer platforms in the late 1980's. The MS-DOS interpreter doesn't work very well on modern Windows machines, especially with most systems shipping with the 64-bit version of Windows, which doesn't support 16 bit applications.

There are a few ways to play AGI games on a modern machine, one of them being to use an emulator. Emulating an MS-DOS system is possible with DOSBox, and emulating other machines like Atari ST, Apple IIgs, Amiga, etc. is also possible with some free emulators. This results in an experience which matches very closely what it would have been like to play the games on these machines 25 years ago.

Another way to play AGI games is to use a Windows port of an AGI interpreter. Agi Player is such an interpreter, which runs on .NET Framework 2.0.

Agi Player adds features not found in the Sierra interpreters, and combines features found only in certain ports of the Sierra interpreter.

Supported Games

Sierra developed several games during the years 1985-1989 using the AGI system. There were 4 major revisions of the system for the PC platform.

• Version 0: Unsupported. Original PC booter version of King's Quest I.
• Version 1: Unsupported. Original PC booter version of King's Quest II and The Black Cauldron.
• Version 2: Supported. Donald Duck's Playground, Christmas Card, King's Quest I, II, III, Leisure Suit Larry I, Police Quest I, Space Quest I and II, Mixed-Up Mother Goose.
• Version 3: Supported. King's Quest IV, Gold Rush!, Manhunter I and II.

On the Atari ST, Amiga and Apple IIgs platforms, only the version 2 and 3 interpreters were used as the games were ported to these systems later on.

Graphical Features

The official interpreters that Sierra shipped for its supported platforms had slightly different styles and features. The color palettes and the fonts were different. In addition, for MS-DOS there were different graphics card that needed to be supported: CGA (2 different palettes of 4 colors), EGA/Tandy (16 colors) and Hercules (2 colors, high resolution). Other platform styles supported by Agi Player are Atari ST, Apple IIgs and Amiga (3 palettes).

Here are screenshots of the different interpreter graphic modes / palette / fonts. These can be cycled through at runtime with CTRL-R.

Scaling

All screenshots were taken using a scaling of 2. This can be configured to be 1 or more. When switching to Hercules mode, the scaling automatically changes to an even number to accomodate the higher resolution needed by that mode.

MS-DOS (EGA/Tandy)

Leisure Suit Larry I, shown here with the EGA/Tandy palette and font.

MS-DOS (CGA)

King's Quest I and King's Quest II, shown here with the CGA palettes and font.

MS-DOS (Hercules)

King's Quest IV and Mixed-Up Mother Goose, shown here with the Hercules high resolution graphics and font. Agi Player supports 3 monochrome colors for Hercules: White, Green (not shown) and Amber.

Atari ST

The Black Cauldron, shown here with the Atari ST palette and font.

Amiga

Police Quest I, shown with the Amiga palette and font.

Apple IIgs

King's Quest III, shown here with the Apple IIgs palette and font.

Input Features

In AGI games, text input happens in real time for all Sierra interpreters except for the MS-DOS (Hercules) interpreter where an input box appeared when the player started typing. For Hercules, the game script pauses while the user enters text, much like it does in Sierra's next generation adventure game system (SCI). This turns out to be an advantage when actions must be taken quickly.

Agi Player supports 3 modes of input, regardless of the graphical mode that is selected (EGA, CGA, Hercules, Amiga, Atari ST, Apple IIgs). The 3 modes are: classic, input box, word list.

Classic

Classic mode is the real time mode that was used in the majority of Sierra AGI interpreters. The player can type in text at the same time as the main character and NPCs move on the screen.

Input box

Input box mode is the paused mode that was used in the Hercules Sierra AGI interpreter, and was later used in SCI games. When the input box is on screen, the game script no longer executes, giving the player all the time necessary to type in the text.

Word list

Word list is a mixed mode where you can hit the ctrl key which brings up a dialog that lets you select a word to add to the input. When the word list is on screen, the game script no longer executes, giving the player all the time necessary to select the desired word.

Audio Features

Tandy 4-channel

Tandy sound is fully supported on MS-DOS, Atari ST and Amiga games.

Apple IIgs MIDI and Waveform

Apple IIgs sound is NOT supported at this time (only applicable to the Apple IIgs versions of the games).

Other Features

Skip Startup Question

Some games required the user to answer a question at the start of the game, in order to verify that the user has the game manual or is of appropriate age due to mature content.

For the following games, the question can be automatically skipped. This option is enabled in the Agi Player configuration.

• Gold Rush!
• King's Quest IV
• Leisure Suit Larry I (age quiz)
• Manhunter: New York

This is what happens when you answer incorrectly in Gold Rush!

Zip Format Support

Agi Player can read games uncompressed in subfolders, or compressed in zip archives.

Requirements

Agi Player runs on the .NET Framework 2.0, and uses the SDL library for graphics, input and sound. SharpZipLib is used to support games that are compressed using the zip file format. The necessary libraries are distributed with Agi Player, so the only requirement is that the .NET Framework 2.0 (or later) be installed.

Download

Want to try it out? Agi Player is now available on GitHub at https://github.com/huguesv/AgiPlayer/releases/latest.