Legendary Pokemon: Weekly Mechanics

Move Data Structure

Arty2 — 2005-11-06T07:34:40+02:00

Introduction

This article provides detailed documentation on the Move data structures in the GBA games. Move names are stored elsewhere.

If you have something to add feel free to comment and I'd be happy to see people contributing to these articles. After every article will follow some related links that will help you get additional information.

Always remember that ROM images are illegal if you do not own the actual game and should only be used for personal backup reasons. If you like a game, please buy it and help the producers make new games.

Specs.

A base stats structure is a 34-byte piece of data in the Advanced Generation games.

Move Data Structure
Data	Type	Description
Effect	byte	This is the move's effect number. Some moves share the same effect number. Effectless moves have an Effect number of 0x00.
Base Power	byte	This is the move's Base Power which is used when calculating inflicted damage.
Type	byte	This is the move's Type.
Accuracy	byte	This is the move's accuracy. Divide this value by 256 to get a % accuracy. An accuracy of 0x00 means that it will never fail.
PP	byte	The move's base Power Points.
Effect Accuracy	byte	This is the effects's accuracy. Divide this value by 100 to get a % accuracy. An accuracy of 0x00 means that the effect will always occur.
"Affects Whom"	byte	This determines who the move will hit on a 2on2 battle
Priotiry	byte	Priority determines the move's speed, for example Extremespeed will always hit first. The byte is signed which means that it can be either positive or negative. The higher the number is, the faster the move is.
Special Flags	byte	A group of bit level flags that determine whether the move is affected by items such as King's Rock or Brightpowder etc. See below for more.
Padding	3 bytes	Always equals 0000. It is used as a divider/padding between the data entries.

Additional References

Types (decimal)

00  Normal      09  ???
01  Fighting    10  Fire
02  Flying      11  Water
03  Poison      12  Grass
04  Ground      13  Electric
05  Rock        14  Psychic
06  Bug         15  Ice
07  Ghost       17  Dark
08  Steel

"Affects Whom" table

Note than only Spikes has a value of 0x40.

0x00  Selected target
0x01  Last opponent who moved
0x02  Unused
0x04  Random target
0x08  Both opponents
0x10  User
0x20  Both opponents and partner
0x40  Opponent field
0x80  Unused

Special Flags

Format (bit level): 00?? ????

0  Empty
0  Empty
?  1: Affected by King's Rock
?  1: Affected By Brightpowder

?  1: Affected by Snatch (Stat Altering)
?  1: No Damage For Opponent
?  1: Affects Opponent   0: Affects User
?  1: Physical Contact (Touch)

Sound moves

Moves that make sound and are therefore negated by the Soundproof ability.

It is unknown where this data is located.

Maximum PP

maxPP = floor((PP*20/100)*3 + PP)

Signed byte

Use this function to convert the Priority value to a readable number.

function signedbyte($number) {
	if ($number < 128) { return $number; }
	return $number-256;
}

Pokedex Data Structure

Arty2 — 2005-11-04T16:09:33+02:00

Introduction

This article provides detailed documentation on the Pokédex data structures in the GBA games.

Some might notice that the following article looks like Bulbapedia's related page; I started that one page and fellow Bulbapedia editors are free to take more details from this one article and add it to Bulbapedia. Most stuff is self-explicatory but let's get into detail.

Specs.

A base stats structure is a 34-byte piece of data in the Advanced Generation games.

Pokédex Data Structure
Data	Type	Description
Padding	byte	Always equals 0x00.
Name	12 bytes	This is the Pokémon's species/nickname. It is always in capital letters and possible empty letters are filled with 0x00. The last byte is a normal slash /. (TINYRACCOON/ for example)
Height	2 bytes	This is the Pokémon's height. It is stored in decimetres (1/10 metres) and converted to other units with in-game functions.
Weight	2 bytes	This is the Pokémon's weight. It is stored in hectogrammes (1/10 kilogrammes) and converted to other units with in-game functions.
Description pointer start	4 bytes	These show the game where the description for that Pokémon is. The MSB byte is always set to 0x08, which matches a BRANCH instruction (B) in assembly. If a pointer looks like 0x12345608 (in hex) then the location is 0x563412.
Description pointer end	4 bytes
Pokémon scale	2 bytes	This is the Pokémon's scale used in the compare size function.
Pokémon offset	2 bytes	This is the Pokémon's offset used in the compare size function.
Trainer Scale	byte	This is the Trainer's scale used in the compare size function.
Trainer Offset	1 bytes	This is the Pokémon's offset used in the compare size function.
Padding	byte	Always equals 0x0000.

Functions

Here follow some functions that are pretty similar to the ones used in the games.

Centimetres to Feet/inches

feet = (round($value/0.254)-$inches)/12 inches = (round($value/0.254)%12)

Hectogrammes to libres

round(($value)*2.20459)/10

Size compare

This returns the picture's height/width in Size Compare Mode.

x = floor(64*256/scale)

Note: 64pixels is a standard sprite size.

The offsets' true use is not confirmed but they sure affect the placement of the Pokémon's sprite. A Pokémon's Levitate ability or Flying type, also seems to have something to do with the sprite's placement.

Base Stats Structure

Arty2 — 2005-10-20T11:21:26+02:00

Introduction

Each Pokémon has some preset base stats, that determine its potential and power. It has also at least one preset type, a catch rate, gender, EP yield etc.

Specs.

A base stats structure is a 28-byte piece of data in the Advanced Generation games.

Base Stats Structure
Data	Type	Description
Base HP	byte	The Pokémon's base HP used to calculate its stats.
Base Attack	byte	The Pokémon's base Attack used to calculate its stats.
Base Defense	byte	The Pokémon's base Defense used to calculate its stats.
Base Speed	byte	The Pokémon's base Speed used to calculate its stats.
Base Special Attack	byte	The Pokémon's base Special Attack used to calculate its stats.
Base Special Defense	byte	The Pokémon's base Special Defense used to calculate its stats.
Type 1	byte	The first Type of Pokémon of the species.
Type 2	byte	The second Type of Pokémon of the species. Matches the first if it only has one Type.
Catch Rate	byte	The Catch Rate used to calculate the probability of catching a wild Pokémon of that species. The higher the value is, the easier it is to capture the Pokémon.
Base EXP	byte	The Base Experience used when calculating the gained EXP. Points when defeating a Pokémon of that species.
Effort Points yield	word	The amount and type of Effort Points gained when defeating a Pokémon of that species.
Held Item 1	word	Wild Held Item number 1 with a Probability of 50%.
Held Item 2	word	Wild Held Item number 2 with a Probability of 5%. When this value matches with the previous one, then the Probability is 100%.
Gender	byte	The value that determines a Pokémon's gender. It represents the rate of females versus males of the species. 0x255 is Genderless, 0x254 is 100% female and 0 is 100% male.
Base Egg Steps	byte	Determines the number of steps that must be taken before an Egg of the species hatches. ActualEggSteps = BaseEggSteps*256.
Base Tameness	byte	The tameness value of a Pokémon of that species has when caught/traded.
Growth Group	byte	This value determines how fast a Pokémon of that species will level up.
Egg Group 1	byte	The first Egg Group a Pokémon of the species belongs to.
Egg Group 2	byte	The second Egg Group a Pokémon of the species belongs to. Matches the first if it only belongs to one Egg Group.
Ability 1	byte	The first Ability a Pokémon of the species may have.
Ability 2	byte	The second Ability a Pokémon of the species may have. If none then the value equals 0.
Safari Zone Flag	byte	Determines rate at which Pokémon of the species flee when encountered in the Safari Zone. Only Pokémon that appear in the Safari Zone have this flag.
Color	byte	The Pokémon's Pokédex color.
Padding	word	Always equals 0000. It is used as a divider/padding between the data entries.

Additional References

Types (decimal)

00  Normal      09  ???
01  Fighting    10  Fire
02  Flying      11  Water
03  Poison      12  Grass
04  Ground      13  Electric
05  Rock        14  Psychic
06  Bug         15  Ice
07  Ghost       16  Dragon
08  Steel       17  Dark

Effort Points Yield (word/bytes reversed)

0000   11     11     11   11   11   11    (binary)
empty  SPDEF  SPATK  SPD  DEF  ATK  HP

Gender

x = ♀, y = ♂, n = gender value

x = floor(n/254)*100

y = 100 - x

Growth Group (decimal)

0   1,000,000   Medium-Fast
1     600,000   Erratic
2   1,640,000   Fluctuating
3   1,059,860   Medium-Slow
4     800,000   Fast
5   1,250,000   Slow

Egg Groups (decimal)

01  Monster   09  Water 3
02  Water 1   10  Mineral
03  Bug       11  Inteterminate
04  Flying    12  Water 2
05  Ground    13  Ditto
06  Fairy     14  Dragon
07  Plant     15  No Eggs
08  Humanshape

Color

0  Red     5  Brown
1  Blue    6  Purple
2  Yellow  7  Gray
3  Green   8  White
4  Black   9  Pink

Basics

Arty2 — 2005-09-30T09:25:12+02:00

Introduction

This is the first article in my weekly column about game mechanics. The first few articles will be about data patterns in the GBA games (most are similar with older ones) and then shall follow some articles about specific game functions. Here are a few bits of knowledge you will need to know in order to understand future articles. Note that I am not a programmer myself but I’ll try to pass on the few things I know many of them cannot be found on the internet (unfortunately).

Basics

First, there is the bit, which has two possible values, on or off, true or false, 1 or 0; exactly like a light switch. You may know that the common numeral system is called decimal, because it uses ten digits, 0-9. Normally, when a number grows too large it overflows to the left such as 09 to 10 and 099 to 100.

There are a few more systems including binary and hexadecimal (hex), which we are going to analyse here.

Hexadecimal includes the following digits: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F. It overflows in the same way as in decimall: 0F to 10 and 0FF to 100. Same applies for binary but binary has only two digits: 0 and 1 (just like a bit). In binary, 0 = decimal 0 and 1 = decimal 1 but 10 = decimal 2, 100 = decimal 4 and 1000 is decimal 8. Add 1 to 10 and you have 11 = decimal 3. Now lets learn how to convert from binary to hex. For example have the following number: 1000101001010011. Now we are going to break it into sets of four: 1000 1010 0101 0011. 1000 is easy to convert, it’s just 8 (see above) but what about 1010? Consider the following table:


   8 4 2 1
   1 0 1 0

You can see that 8 and 2 are on (have a 1 instead of 0), so 8+2 = 10 (decimal) = A (hex). We continue doing the same with the rest of the number and we have the following:


   1000 1010 0101 0011   (binary)
     8   10   5    3     (decimal)
     8   A    5    3     (hexadecimal)

Of course, you can always use a scientific calculator (or your Windows/Linux/Mac calculator of choice) for these conversions but knowing the above makes the whole thing easier to deal with. Now here's how PC's and Nintendo games work: they swap the high byte and low byte of two byte values. So, whereas the highest move's number is 0AFF, then in the ROM data, it will be stored with the 0A and FF reversed. So our previous example will be stored as 538A, or if our number was something like 10EAB65 it would be stored as 65AB0E01 (mention that 1 is actually 01).

Another interesting fact is that GameBoy (and some other) games always round down when it comes to calculating things. We'll call that floor() while ceil() will be our round-up name and round() the normal rounding we learnt in highschool.

Here's a few programs you are going to need before our next article:

Game oriented hex editor (for example Thingy32)
General hex editor (for example ICY Hex Explorer)
Relative searcher (for example SearchR X)

Legendary Pokemon: Weekly Mechanics

Move Data Structure

Introduction

Specs.

Additional References

Types (decimal)

"Affects Whom" table

Special Flags

Sound moves

Maximum PP

Signed byte

Related links

Pokedex Data Structure

Introduction

Specs.

Functions

Centimetres to Feet/inches

Hectogrammes to libres

Size compare

Related links

Base Stats Structure

Introduction

Specs.

Additional References

Types (decimal)

Effort Points Yield (word/bytes reversed)

Gender

Growth Group (decimal)

Egg Groups (decimal)

Color

Related links

Basics

Introduction

Basics

Related links