The most recent copy of this document can be obtained from the Tower of Bab-Il
(http://minitrue.weyland-yutani.net/tower/index.html).
This document uses normal bit order (bit 0 is the least significant bit).
Enemies in this game have their actions when in battle determined by their
attack sequence(s), rather than being determined at random or by an AI
(Artificial Intelligence). The attack sequence data is stored in an
appallingly complex and inefficient manner.
In order to determine what a monster does, first look at the attack sequence
group number in the main monster data. The attack sequence group data is
stored from 76230 to 767FF. This data consists of a series of attack sequence
groups, with each stored right after the other and absolutely no offset table
or any other means of finding one quickly. Instead, the game code reads the
bytes one at a time until the number of FF bytes specified by the attack
sequence group number has been read. The attack sequence group data follows
immediately afterwards.
So the attack sequence group data is just a list of FF-terminated lists,
right? Well, not quite. In one of the groups, FF is both the list terminator
and the attack sequence number (see below).
Each attack sequence group is made of from one to ten two byte entries. The
first byte determines under what condition(s) the attack sequence specified by
the second byte will take place.
The first byte of the attack sequence group is looked up in yet another list
that extends from 76800 to 773FF. This list is another list of lists; each of these sub-lists consists of
from one to three condition bytes terminated by an FF. Once again, the game
code must walk down the list one byte at a time, looking for those FFs.
Presumably, these bytes represent conditions that must all be met for the
specified attack sequence to be used. The condition bytes are looked up in a
table from 76900 to 76AFF. Each table entry is four bytes. I don't know the
exact meaning of these bytes yet.
The second byte of the attack sequence group is looked up in still another
list of lists. Once again, the game code must walk through the list, counting
FF bytes as it goes. The individual lists are attack sequences (finally!),
consisting of a number of one or two byte attack codes and terminated by an FF
byte. Each attack sequence can be up to 3C bytes long. There are actually two
of these attack sequence lists. The attack sequence data from 76B00 to 773FF
is used for most of the monsters, but there is a second list of attack
sequence data from 738C0 to 73CCF that's used for some lunar monsters. I don't
know how exactly the game determines which to use.
Here are the meanings of the known attack codes:
00-30 The byte is the spell number of a spell.
31-5E The byte is the spell number of a spell + 30. So no, you can't make
monsters cast call magic.
5F-BF The byte is the spell number of an enemy special ability.
C0-E7 The byte is the number of a player menu command + C0. So C0 is Fight
(which makes the monster do a normal physical attack), C5 is Dummy/ankoku
(the Dark Knight's dark energy wave attack), C6 is Jump, etc. A lot of
commands won't work properly when a monster tries to do them. Command
number 21 (or attack byte E1) is worthy of special mention, as it does
absolutely nothing. Certain special attack codes seem to require that they
be followed by a spell or command, and E1 is often used for this purpose.
E8 XX Change the monster's creature type byte to XX.
E9 XX Change the monster's physical attack values to the triplet specified by
XX.
EA XX Change the monster's physical defense values to the triplet specified by
XX.
EB XX Change the monster's magical defense values to the triplet specified by
XX.
EC XX The 16-bit number at offset 60-61 in the monster's data record that is
derived from it's agility and determines its base speed is modified. The
lower seven bits of XX are multiplied by the existing speed value,
multiplied by one hundred, and divided by one thousand. The result of all
this is added to the existing value, or subtracted instead if the MSB of
XX is set. Remember, lower values at offset 60-61 mean a faster speed.
ED XX Set the monster's elemental defenses as if the elemental defense byte in
the monster data had been set to XX.
EE XX Set the monster's spell power to XX.
EF XX Set the monster's weaknesses as if the weakness byte in the monster data
had been set to XX.
F0 XX Changes the monster graphic. I don't know exactly how this works.
F1 XX Displays battle dialogue XX.
F2 XX As F1 XX, but surpresses the name of the next attack(?)
F3 XX Change music to XX.
F4-F7 XX Changes which attack sequences and/or reflexes are being used
somehow. I'm not yet sure quite how this works.
F8 I don't know what this does, or even if it takes a parameter or not.
F9 XX Set the target(s) of the next attack, as specified by XX:
00-15 the character with that character id
16 self
17 all monsters
18 all other monsters
19 all monsters of the first monster type in the encounter
1A all monsters of the second monster type in the encounter
1B all monsters of the third monster type in the encounter
1C front row of the party
1D back row of the party
1E one paralyzed monster
1F one sleeping monster
20 one charmed monster
21 one criticaly injured monster
22 one random monster or character
23 one random monster or character other than self
24 random monster
25 random monster other than self
26 random front row party member
27 random back row party member
28 whole party
29 all dead monsters
FA I don't know what this does, or even if it takes a parameter or not.
FB Seperates the attack codes in an attack chain.
FC Ends an attack chain.
FD Starts an attack chain.
FE Provides a pause in between attacks, causing the monster to wait its turn
to do the next attack. This is used to seperate almost all non-chain
attacks.
FF Of course, this ends the sequence. When the monster reaches the end of its
sequence, it repeats. Also has the effect of FE.
An "attack chain" is a series of attacks that have no breaks between them and
the display of any damage is postponed until the end of the chain, such as the
double hits many monsters do and Dark Elf's little "ME ATTACK YOU!" routine.
In my opinion, the data storage format described above is an astonishing mass
of idiocy. For each monster in the encounter (and there can be up to eight),
the game has to walk through a massive list, then for every byte in that list
entry once it has been found (and there can be up to twenty) it must walk
through one of several other lists. And if the monster has any reflexes, it
must do all that a second time as well. And the way the attack sequences were
divided into two data areas is rather hackish. I don't yet know how it chooses
which one to use, but when I once tried to add a lunar monster (EvilMask) to
an encounter on earth, it used the wrong attack sequence data.
If I were to rewrite the monster loading code, I would do things a little
differently. For one thing, I'd seperate the attack sequence and group data
based on whether they were reflexes or standard attacks. And I'd use offset
tables to reduce the loading time (not to mention make hacking the game
easier!) Some day I may in fact do all this and release an IPS patch with the
improved code, but don't hold your breath.