Comments on Chaos
Sean A Irvine
Chaos Breakdown
===============
Sean Irvine (sir...@cs.waikato.ac.nz)
Dept. of Mathematics
University of Waikato
Private Bag 3105
Hamilton
NEW ZEALAND
There has been much reminiscing over the last year about the ZX Spectrum
game "Chaos: Battle of the Wizards" (Julian Gollop, Games Workshop, 1984)
in a variety of forums. This role-playing game spurned the sequel
"Lords of Chaos" on a number of platforms, but many people continued to
yearn for clones more like the original for other platforms. Recently a
clone for PC was produced called Morkin2, there is also rumoured to be
a clone for the Atari ST. I have never seen either of these clones and so
cannot comment on them. I am the author of a clone for the Commodore
Amiga, and I'll say a little bit about my clone towards the end.
In writing the clone (and even before then) I disassembled various parts
of the Spectrum Chaos and thereby obtained considerable detail about its
operation, and this I believe gives me the qualification to make some
comments about Chaos. I should say that I have never spoken to Julian
Gollop about any of the things included here, so a few things are just
mere speculation on my part. Further, most of the effort was carried out
several years ago, and as such my memory is a little hazy about a few of
the details. In particular I can clarify the situation with regard to a
few pieces of folklore (like the unused sprites and spells) and introduce
some new bits and pieces that I have not previously seen in the literature.
I used to play Chaos extensively on the Spectrum with my brothers. However,
we always wanted to play longer and longer versions of the game. To this
end we proclaimed a number of `house rules' like `thou shall not kill a
human wizard until all its creations have been killed' in an effort to
make the game last longer. Unfortunately, this caused most games to result
in a draw, and led me to make my first hacks in the Chaos code. It was a
trivial matter to alter the code so that we could restart the game and
continue on from where we left off. Then we had the perennial problem that
fire would engulf the entire screen, so I wrote an editor which enabled
the contents of the screen to be altered. The editor also allowed one to
change the number of spells allocated at the outset and other things of a
similar vain. The mechanism for some of these will be discussed below.
I'm not exactly sure what happened to my fabled editor, it is probably
collecting dust in some remote corner of a closet in my parent's house;
but if I ever find it I will upload it to a suitable site.
There is another editor distributed with Emulate magazine that allows
inspection and alteration of graphics and text within Chaos.
Some parts of this document are necessarily technical. Remember when
attempting any of the hacks suggested here that you should probably
work on a copy of Chaos, so that you can resurrect the original game
when required.
Anyway the purpose of this article is to describe in detail some of the
inner workings of Chaos, and a nice easy place to start is with the sprites
and the observation of sprites in the code which are not used in the game.
The addresses I give are in decimal.
Sprites
=======
The sprites are dispersed at a number of locations in the code as listed
below. Each sprite is coded as four characters in the usual UDG method.
32551: The graphic for the [S] cursor.
32944: The graphics for modified wizards, including wizards with
magic swords, bows, knives, shields, armour, and wings.
41484: The twirl used during casting.
41797: Explosion effect.
48951: Attack effect, exploding circle.
49443: Result of dragon breath effect.
49981: Various cursors (empty box, wings, and arrows).
60241: Graphics for the creatures and other objects like wall, note
this continues all the way to 64820 where the wizard descriptions
begin.
64820: Start of the graphics for the eight different wizards.
The character set information starts at 55560. PostScript images of all
the sprites in Chaos are available on my web page:
http://www.cs.waikato.ac.nz/~sirvine/
As has been noted by several people there are a number of graphics in here
which do not appear in the actual game. In particular their are the
infamous troll graphics at 62515, 62547, 62579, 625747, and 62611. There
is also a graphic for a dead vampire (in the game undead's never result
in corpses) at 61331 and for what can only be described as dead gooey
blob at 60627. This can actually be verified by forcing a piece of
this stuff onto the screen where it will then sprout living pieces of
blob. Each creature has either one (e.g. spectre), three or four images.
There is also what must be a dead image for a spectre which again never
occurs in the game.
A table starting at ~58436 gives the name, statistics, and location of the
sprites for each object in the game. Entries are of variable length and give
first the name, then the stats, the five lots of 3 bytes that describe
the image location (machine address) and attribute to use for that image.
Note that this table is not in the same order as the actual internal
order used by the rest of the program. In particular, this table does
contain an entry for the troll which is never used anywhere else in the
program. A typical entry is shown below (from address 59371):
SKELETON 3 5 0 2 1 3 4 6 255 17 63284 71 63316 71 63348 71 63316 71
This gives the information for a skeleton and indicates that all its
sprites should be drawn with attribute 71 (bright white) and that its
image data is located at 63284, 63316, 63348 and 63316.
For the sake of completeness I include the relevant statistics
here for your reference. The columns of numbers are: combat, ranged
combat, range, defence, movement allowance, magical resistance,
manoeuvre, ???, law/chaos rating, overall strength (?).
0 Nothing
1 Nothing
2 King Cobra 4 0 0 1 1 6 1 8 1 30
3 Dire Wolf 3 0 0 2 3 7 2 8 -1 12
4 Goblin 2 0 0 4 1 4 4 8 -1 12
5 Crocodile 5 0 0 6 1 2 2 7 0 34
6 Faun 3 0 0 2 1 7 8 7 -1 20
7 Lion 6 0 0 4 4 8 3 5 1 38
8 Elf 1 2 6 2 1 5 7 6 2 26
9 Orc 2 0 0 1 1 4 4 9 -1 21
10 Bear 6 0 0 7 2 6 2 5 1 23
11 Gorilla 6 0 0 5 1 4 2 6 0 18
12 Ogre 4 0 0 7 1 3 6 6 -1 23
13 Hydra 7 0 0 8 1 4 6 4 -1 36
14 Giant Rat 1 0 0 1 3 8 2 9 0 13
15 Giant 9 0 0 7 2 6 5 3 1 23
16 Horse 1 0 0 3 4 8 1 8 1 21
17 Unicorn 5 0 0 4 4 9 7 5 2 16
18 Centaur 1 2 4 3 4 5 5 6 1 23
19 Pegasus 2 0 0 4 5 6 7 5 2 16
20 Gryphon 3 0 0 5 5 5 6 5 1 10
21 Manticore 3 1 3 6 5 6 8 3 -1 13
22 Bat 1 0 0 1 5 9 4 7 -1 8
23 Green Dragon 5 4 6 8 3 4 4 0 -1 32
24 Red Dragon 7 3 5 9 3 4 5 0 -2 34
25 Golden Dragon 9 5 4 9 3 5 5 0 2 27
26 Harpy 4 0 0 2 5 8 5 5 -1 13
27 Eagle 3 0 0 3 6 8 2 6 1 14
28 Vampire 6 0 0 8 4 6 5 1 -2 40
29 Ghost 1 0 0 3 2 9 6 4 -1 15
30 Spectre 4 0 0 2 1 6 4 5 -1 15
31 Wraith 5 0 0 5 2 4 5 4 -1 10
32 Skeleton 3 0 0 2 1 3 4 6 -1 17
33 Zombie 1 0 0 1 1 2 3 4 -1 25
34 Blob 1 0 0 0 0 0 0 0 0 40
35 Fire 0 0 0 0 0 0 0 0 0 12
36 Magic Wood 0 0 0 5 0 0 9 6 2 250
37 Shadow Wood 2 0 0 4 0 0 9 4 -2 30
38 Magic Castle 0 0 0 0 0 0 0 0 0 50
39 Dark Citadel 0 0 0 0 0 0 0 0 0 50
40 Wall 0 0 0 0 0 0 0 0 0 30
41 Wizard1
42 Wizard2
43 Wizard3
44 Wizard4
45 Wizard5
46 Wizard6
47 Wizard7
48 Wizard8
Notice the careful ordering of this table with all the flying creatures
grouped together, all the mounts grouped together, and all the undead
creatures grouped together. This leads to numerous simplifications in the
coding of the game, that are best appreciated by delving into the code
itself.
Text Messages
=============
Apart from the names of the creatures and wizards there are two other
groups of text messages in Chaos. These start at locations 34905 and
53195 respectively. A table starting at 34825 gives the addresses and
lengths for the first set of messages, a similar table starting at
52691 gives the same information for the second group of messages.
The actual subroutines to print these messages are found at 34799 and 47867.
When called BC holds the screen address and A holds the message
number.
The messages in the first group are:
CHAOS -THE BATTLE OF WIZARDS
By Julian Gollop
How many wizards?
(Press 1 to 8)
PLAYER
Computer controlled?
YES
NO
Level of computer wizards?
Enter name (12 letters max.)
(Press Y or N)
Which colour?
Which character?
1
2
3
4
5
6
7
8
(Press 2 to 8)
NEW SPELL FOR
THE CONTEST IS DRAWN BETWEEN
THE WINNER IS:
^^^^^^^^^^^^^^^^^
The messages in the second group are (the numbers are
the internal code for the message):
0--47 <names of creatures and wizards>
49 (ASLEEP)
50 (DEAD)
51 DISMOUNT WIZARD? (Y OR N)
52 ENGAGED TO ENEMY
53 OUT OF RANGE
54 (FLYING)
55 'S TURN
56 MOVEMENT POINTS LEFT=
57 UNDEAD-CANNOT BE ATTACKED MOVEMENT
58 RANGE=
59 RANGED COMBAT,RANGE=
60 NO LINE OF SIGHT
61 PRESS ANY KEY
62 KNIFE
63 SWORD
64 ARMOUR
65 SHIELD
66 FLYING
67 SHADOW
68 MOUNT
69 UNDEAD
70 (CHAOS
71 (LAW
72 COMBAT=
73 RANGED COMBAT=
74 RANGE=
75 DEFENCE=
76 MOVEMENT ALLOWANCE=
77 MANOEUVRE RATING=
78 MAGIC RESISTANCE=
79 CASTING CHANCE=
80 10
81 SPELLS=
82 ABILITY=
83 'S SPELLS
84 SPELL FAILS
85 SPELL SUCCEEDS
86 IS THE WINNER
87 PRESS KEYS 1 TO 4
88 PRESS '0' TO RETURN TO MAIN MENU
89 1.EXAMINE SPELLS
90 2.SELECT SPELL
91 3.EXAMINE BOARD
92 4.CONTINUE WITH GAME
93 DISBELIEVE
94 ILLUSION? (PRESS Y OR N)
95 'S CREATIONS
96 MAGIC FIRE
97 GOOEY BLOB
98 LIGHTNING
99 VENGEANCE
100 DARK POWER
101 DECREE
102 JUSTICE
103 LAW-1
104 LAW-2
105 CHAOS-1
106 CHAOS-2
107 MAGIC SHIELD
108 MAGIC ARMOUR
109 MAGIC SWORD
110 MAGIC KNIFE
111 MAGIC BOW
112 BLIND
113 MAGIC BOLT
114 TEMPEST
115 RAISE DEAD
116 TELEPORT
117 SUBVERSION
118 TURMOIL
119 DEAD REVENGE
120 CONSECRATION
121 DISPEL
122 COUNTER SPELL
123 MAGIC WINGS
124 MAGIC SLEEP
125 SHADOW FORM
Internally these are numbered starting at zero, but because of the
objects in the game taking the first 48 positions the message
(ASLEEP) is code 49, (DEAD) is code 50, etc. As far as I know the
messages (ASLEEP), BLIND, TEMPEST, TELEPORT, DEAD REVENGE, CONSEC-
RATION, DISPEL, COUNTER SPELL, and MAGIC SLEEP do not occur in play-
ing the game. The (ASLEEP) can be made to appear by fiddling with the
owner table as described further below.
This finishes the discussion of what one might expect to discover
after a few hours of hacking around in the code. I will now move
onto some more advanced material.
Spells
======
There is a table which starts at 32096 which consists of a series
of 7 byte records in the format: internal object number, ?(1),
twice the maximum cast distance, effect on chaos/law indicator, ?,
address of routine to cast this spell:
32096 93 9 255 0 0 Disbelieve
32103 2 8 3 1 18 CreatureCast
32110 3 8 3 -1 18 CreatureCast
32117 4 8 3 -1 18 CreatureCast
32124 5 7 3 0 18 CreatureCast
32131 6 7 3 -1 18 CreatureCast
32138 7 5 3 1 18 CreatureCast
32145 8 6 3 2 18 CreatureCast
32152 9 9 3 -1 18 CreatureCast
32159 10 5 3 1 18 CreatureCast
32166 11 6 3 0 18 CreatureCast
32173 12 6 3 -1 18 CreatureCast
32180 13 4 3 -1 18 CreatureCast
32187 14 9 3 0 18 CreatureCast
32194 15 3 3 1 18 CreatureCast
32201 16 8 3 1 18 CreatureCast
32208 17 5 3 2 18 CreatureCast
32215 18 6 3 1 18 CreatureCast
32222 19 5 3 2 18 CreatureCast
32229 20 5 3 1 18 CreatureCast
32236 21 3 3 -1 18 CreatureCast
32243 22 7 3 -1 18 CreatureCast
32250 23 0 3 -1 18 CreatureCast
32257 24 0 3 -1 18 CreatureCast
32264 25 0 3 2 18 CreatureCast
32271 26 5 3 -1 18 CreatureCast
32278 27 6 3 1 18 CreatureCast
32285 28 1 3 -2 18 CreatureCast
32292 29 4 3 -1 18 CreatureCast
32299 30 5 3 -1 18 CreatureCast
32306 31 4 3 -1 18 CreatureCast
32313 32 6 3 -1 18 CreatureCast
32320 33 8 3 -1 18 CreatureCast
32327 97 8 13 -1 18 CreatureCast
32334 96 7 13 -1 18 CreatureCast
32341 36 7 17 1 17 Trees&Castles
32348 37 3 17 -1 18 Trees&Castles
32355 38 4 17 1 23 Trees&Castles
32362 39 4 17 -1 23 Trees&Castles
32369 40 7 13 0 12 Wall
32376 112 9 13 0 18 Lightning
32383 112 9 13 0 18 Lightning
32390 98 9 9 0 18 Lightning
32397 98 9 9 0 18 Lightning
32404 99 7 30 -1 12 DarkPowerEtc
32411 101 7 30 1 12 DarkPowerEtc
32418 100 4 30 -2 11 DarkPowerEtc
32425 102 4 30 2 11 DarkPowerEtc
32432 107 6 0 1 23 MagicShield
32439 108 3 0 1 23 MagicArmour
32446 109 3 0 1 16 MagicSword
32453 110 6 0 1 16 MagicKnife
32460 111 4 0 1 17 MagicBow
32467 123 4 0 0 14 MagicWings
32474 103 7 0 2 5 ChaosOrLawSpell
32481 104 5 0 4 6 ChaosOrLawSpell
32488 105 7 0 -2 5 ChaosOrLawSpell
32495 106 5 0 -4 6 ChaosOrLawSpell
32502 125 6 0 0 18 ShadowForm
32509 117 9 15 0 18 Subversion
32516 117 9 15 0 18 Subversion
32523 115 4 9 -1 18 RaiseDead
32530 115 4 9 -1 18 RaiseDead
32537 118 9 20 -1 17 Turmoil
32544 118 9 20 -1 17 Turmoil
The second field could perhaps have something to do with the
colour of the spell? I am unsure what the fifth column could
be for.
Other important addresses: 35241 (level of computer players),
37203 (current chaos/law indicator), 37221 (spell success flag),
37755 (spell selected), 38862 (number of attempts for current
spell, e.g. =4 for a wall spell), (44050--3) position of cursor
on board.
Object Tables
=============
The main state information of the game is stored in a series
of 320 byte tables starting at 57375. The first table contains
the object code for the item in each cell of the screen. The
second table is for ?. The third table contains the current
animation value. The fourth table contains the owner numbers.
Each table also contains space for objects in what is normally
the border.
In the animation table value 0 to 3 are the position in the
animation sequence, 4 is the corpse, and 5 is for asleep (?).
Game Startup
============
The BASIC program starts Chaos by jumping to location 32000,
but in fact the first instruction executed there is merely a
jump to 35321 where the real initialization begins. Roughly,
speaking the initialization runs as follows:
i) Make border blacks and set up ATTR_T, ATTR_P, MASK_P, and
PFLAG system variables.
ii) Disable interrupts.
iii) Clear the screen.
iv) Clear various buffers (by replacing all memory from 35344
through to 35395 the game can be made to continue from its
previous state).
v) Welcome screen, input number of players and wizard level.
vi) Input each players name in turn, choose sprites.
...
(I never got much further, but presumably there is some
initialization for spells that follows here somewhere.)
Miscellaneous Routines
======================
The following are for the most part not very useful to use from
basic since they assume all sorts of things about the registers,
interrupts, etc. But I include them here to aid anybody else
trying to hack parts of chaos.
33536 Gets the address of the wizard name buffer of the current
player.
34543 Start point of the turmoil routine. Maybe someone else
could examine this and determine why it causes the game
to crash sometimes.
35248 Input a number from the keyboard.
36762 Routine to check for new spells.
36939 Random number generator (?) [the last random number
produced is stored at 36986]
37104 Draw a wizard.
38819 Test if a spell cast succeeded.
38842 Print message saying spell succeeded.
39285 Main casting routine for creatures.
40784 Grow gooey blobs and fires.
47854 Print text of length E from HL to BC.
47867 Print a message from the second set.
47959 Draw the border.
48278 Handle the I key and numbers.
48855 Blank the bottom of the screen.
50099 Information routine.
50670 Clear screen.
57103 Master printing routine
57166 Print given object.
57202 Update the screen.
65110 Set standard ROM interrupts.
65120 Set game interrupts (animate the screen). It is quite cool
to actually do a RANDOMIZE USR 65120 while in BASIC, you then
get Chaos animating the screen over BASIC, quite freaky.
Miscellaneous Pokes
===================
These are easily done using a Multiface 2 or with some emulators.
However, it is possible to make these pokes by loading Chaos and
not letting it run or alternatively by playing the game once and
then pressing BREAK while the winner/loser screen is shown. You
should then POKE 23606,0; POKE 23607,60 to invoke the standard
character set. Once you have made the desired pokes, you can
start the game by RANDOMIZE USR 32000.
The following is a collection of addresses and what to put there
to cause various effects where x denotes any sensible code.
34171,x: Maximum object code which can be subverted + 1,
standard value = GooeyBlob. Putting 1 here will
make subversion impossible.
34543,201: Disable the turmoil spell (?).
36239,x First spell (disbelieve by default).
39286,x: Number of creatures per cast.
39646,x: Number of trees per cast.
39659,x: Number of castles per cast.
39799,x: Number of pieces of wall per spell.
40120,x: Maximum object code hitable with lightning (?).
40444,x: Number of attempts for Decree and Vengeance.
40455,x: Number of attempts for Justice and dark power.
36173,0; 36178,x: Force each player to have x spells at the start
of the game. Last spell is infinite for x > 21.
36173,21; 36178,20: Normal spell allocation.
36194,5; 36232,12; 36186,0: Make all spells white all the time.
Note: I have not tried those marked (?), but for theoretical reasons
I expect they should work.
Hints to Hackers
================
There are several general techniques which have proven useful
in hacking Chaos. Firstly, look for instructions of the form
CP x, where x is a valid creature code. In this way it is quite
easy to track down all those areas of code potentially related
to, for example, the shadow wood.
Similarly, look for instructions of the form LD A, x and a
nearby call to a print routine. These enable one to locate
code associated with any particular message.
For example searching for a LD A,94 instruction (which might
have to do with "ILLUSION Y/N") yields a few likely candidates.
In fact the relevant occurrence is at 38021. About here is
where the program ask you whether or not you want and illusion.
By replacing the instruction at 38032 with LD A,"N"; NOP you
can prevent the game from ever asking this question.
Amiga Chaos
===========
As promised at the beginning of this document, I will say a little
bit about the clone of Chaos that I have written for the Amiga. In
my clone I have tried to preserve the gameplay of the original
version, and the clone supports all the spells of the original,
except the relatively stupid Chaos and Law spells, and the Shadow
Form spell. But, the number of spells has been greatly expanded,
there are currently over 150 spells. They include my interpretations
of the Sleep, Tempest, Teleport, and many other novel spells. Oh, and
I have a troll as well (along with many other new creatures).
I have retained 16 by 16 pixel imagery for the sprites, but made the
board slightly larger than the original chaos. The original shapes of
most sprites have been retained, but have been enhanced with additional
colour, so that each creature is now multi-coloured.
In addition there is a team play system and independent creatures.
If you own an Amiga and don't already have my clone then you can obtain
it off any one of the Aminet ftp sites. A PostScript manual for the
game (including full details of all the spells is available on my web
page, http://www.cs.waikato.ac.nz/~sirvine/).
If anyone wants to make a serious attempt at porting my Chaos clone
to other platforms I will make my source code available to them.
Currently the source is about 1 MB of C code, but does not rely
heavily on custom Amiga graphics chips, which should alleviate some
of the difficulties in porting to other systems.
aacq...@gmail.com
Guesser
>
> Hey, I've played Chaos for many years. And I wanted to do so with mi children. Unfortunatly, they do not read in english (but yes in spanish). How could I modify the code of Chaos to translate the messages. Does it exist a way to "open" the file in a inteligible text mode, to change some characters? Thank you. Your article is very interesting.
>
Guesser.
bir...@gmail.com
Thanks!
Guesser
> Hi there! I am thinking about makeing a port of this game to amiga. Can u help me with some questions a i have about the game?
>
> Thanks!
>
Guesser
bir...@gmail.com
Did u dissaemble the original spectrum versión or make your own algorithm for the AI of the wizards?
Guesser
> I need to know about AI of computer wizards, just to make the port.
> Did u dissaemble the original spectrum versión or make your own algorithm for the AI of the wizards?
>
Unfortunately I can't help with that question as we don't have any of
the AI code done yet. (or much of the game logic at all really).
bir...@gmail.com
Guesser
> Thanks for all. What tolos are u using to watch zx source code?
>
stepping through code with emulator debuggers for particularly confusing
bits.
bir...@gmail.com
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the OVERCAT [The BEARPAIR are dead, and we are its murderers], lowlife troll,
shyster [pending approval by STATE_TERROR], cripple, sociopath, kook,
smug prick, smartarse, arsehole, moron, idiot, imbecile, snittish scumbag,
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I mark any message from »Q« the troll as stinky
Alexandra Franks
so thankful for the zxnet disassembly and the three decades of community involvement in this thread
i'd advise anyone curious to just jump in - as far as i know there aren't any all-in-one speccy SDKs - but the machine itself was designed to be poked and peeked at and does welcome and reward those with patience. skoolkit and the built-in profiler/disassembler have been super helpful though - i haven't needed more
so right now we're using a single html/js page which requires a random seed, and spits out a pokfile you can just drag into the emulator at the start of the game. i'll list the feature set we're using right now which still provides balanced games - but would also love to hear any other ideas/feedback - i expect to release it before the end of the year but if i can add in anyone's dream feature, i'd be happy to
* full set of 19 spells, properly randomised for both human and computer players
* simple arenas - wizards start with one wall or tree to block turn 0 magic bolts
* found pokes: trees*12, walls*10, castles*2
i've also spent a lot of time on zxnet figuring out how to increase the play area size - i have a poke which basically inserts some pasmo z80 into the main game loop which copies the creature data into the unused assembly portion, fixes all the references and then patches itself out, leaving enough space for a bigger map. was thinking about wrap-around, but leaning towards just 3 extra spaces around the edges. i've traced enough of the code to know it's possible, but annoying :)
happy to share some new suggestions for the remaining zxnet unlabeled vars and routines, and it'd be amazing to hear of any new features people would like to play!
