
	Level 9 Interpreter v2.0
	An interpreter for Level 9 games in any format,
	including Spectrum snapshots.

	Written by Glen Summers
        Atari ST port by Mia Jaap 2002 (mia-jaap.de/software/)

Introduction
------------

During the 1980s a small British company called Level 9, run by two brothers
(Mike and Pete Austin), produced a series of text adventure games for a
variety of computers. These games received considerable critical acclaim and
are probably the best text adventures written for the small cassette based 8
bit computers common in Britain in the 80s.

Level 9 wrote their games using a custom designed system known as "A-Code",
which evolved from games on the 8 bit computers such as the Acorn BBC Model
B, the Sinclair Spectrum and the Commodore 64 to the (then new) 16 bit
machines such as the Amiga and the Atari ST.

From disassembly of Level 9 games there are thought to be four variants of
A-Code, which are detailed below. Thanks go to Paul David Doherty for
analysing the games and producing the table which follows. At present this
interpreter supports v2, v3 and v4 games.

  v1	This was used for the earliest games. Spectrum v1 games had
	black text on a grey background. Games known to be released in
	this format:

		Colossal Adventure	Adventure Quest
		Dungeon Adventure	Snowball
		Lords of Time

  v2	These releases were made between 1984 and 1985 (and usually say
	so in the startup copyright message. This version introduced
	the yellow text on a black background which became standard.
	Games in this format were:

		Return to Eden		Lords of Time
		Red Moon		Erik the Viking
		Emerald Isle

  v3	This format, dated 1986, was used by the largest number of
	releases. These were:

		Worm in Paradise	The Price of Magick
		The Growing Pains of Adrian Mole
		The Jewels of Darkness Trilogy (Colossal Adventure,
		Adventure Quest and Dungeon Adventure released as
		one package)
		The Silicon Dreams Trilogy
		(Snowball, Return to Eden and Worm in Paradise)

  v4	This was used for the Time and Magick Trilogy (Lords of Time,
	Red Moon and The Price of Magick), and all Level 9's new games
        from 1987 onwards:

		Lancelot		Knight Orc
		Gnome Ranger		Ingrid's Back
		Scapeghost


Supported Formats
-----------------

On several machines (such as the Amiga) Level 9 games were distributed as
an interpreter plus a datafile, usually called "gamedata.dat" or something
similar. These games can be played with this interpreter simply by loading
the "gamedata.dat" file.

For the Amiga (and possibly some other formats) the v4 games were released
in three parts, each in a separate data file:

	gamedat1.dat
	gamedat2.dat
	gamedat3.dat

Starting the first game gives a menu from which you can choose which part or
game to play. For this to work the files must have the same basic structure
with a number in it somewhere, e.g. file names

	TimeAndMagick1.dat
	TimeAndMagick2.dat
	TimeAndMagick3.dat

will work.

On other (especially older and smaller) computers the games were distributed
as a single file containing both an interpreter and the game data. Level9
can cope with these files as well, as it automatically searches files for
valid Level 9 games. This however requires that the file not be compressed
in any way. For example, there are several Spectrum snapshots of Level 9
games available which this interpreter can play, but these snapshots must
be in an uncompressed format (e.g. SNA). Commonly snapshots are available in
the compressed Z80 format, but these files can be converted to SNA using the
widely available conversion program "SPConv". Version 1.06 or higher of
"SPConv" is recommended.

This program has been tested on files obtained from Amigas, Spectrums, BBCs,
Commodore 64s, Ataris and IBM PC compatibles.


Meta Commands
-------------

Level9 supports several meta commands, which can be entered on the input
line. These commands are handled by the interpreter rather than being passed
to the game. They are:

  #restore	Loads in a saved position directly, bypassing any
		protection code withing the game.

  #quit		Quits the current game.

  #cheat	Tries to bypass the copy protection code which asks for
		a specific word. This is done by trying every word in
		the game's dictionary. On a slow machine, this can take
		a long time.

  #dictionary	Lists the game dictionary. Press a key to stop the
		listing and return to the input line. Note that the v2
		dictionary appears to have random characters following
		on the end: The original interpreter code to detect the
		end of dictionary does not appear to agree with the
		characters actually at the end.


History
-------

  v2.0	Revised the description of v4 games to include all the post-1987
	games, which are now supported.
	v2 games are also now supported.
	Added meta commands.

  v1.0  First release.


Credits
-------

The Level9 Interpreter was written by Glen Summers, who can be contacted
on email at

	gsummers@physics.ox.ac.uk

This documentation was written by David Kinder, who can be reached at

	kinder@teaching.physics.ox.ac.uk
or	david.kinder@physics.ox.ac.uk

Help, testing and information on the various Level 9 formats was provided by
Paul David Doherty.


The Interactive Fiction Archive
-------------------------------

If you have access to the Internet and are interested in text adventures,
then you can find all sorts of programs and information at The Interactive
Fiction Archive, at the ftp site ftp.gmd.de, in the /if-archive directory.
The latest version of this program can always be found here.
