beanieaxolotl · February 9, 2025 07:40
diff --git a/A2Mx Game Engine documentation.txt b/A2Mx Game Engine documentation.txt
 A2Mx Game Engine
 > The A2Mx game engine is a 2D engine that has been used for platformer, isometric and top-down games, with support for SRAM saving (or passwords), and cutscenes. It was developed by Stéphane Hockenhull[1] (https://rv6502.ca/), with the tools being developed by Benoit Hubert[2].
 > A2Mx is not the confirmed name of the engine, but it could be judging by the names "A2M4" and so on appearing in the ROM.


 > Known games

 	A2M0:
 	- Enchanted - Once Upon Andalasia (last game)

 	A2M1:
 	- Kim Possible 2: Drakken's Demise
 	- Happy Feet
 	- everGirl
 	- Scooby-Doo: Mystery Mayhem (debut)

 	A2M2:
 	- Lizzie McGuire 2 - Lizzie Diaries

 	A2M4:
 	- Chicken Little

 	A2M5:
 	- Ed Edd & Eddy: The Mis-Ed-Ventures

 	A2M7:
 	- The Sims 2: Pets

 	A2MR:
 	- Monster House

 	A2MT:
 	- Drake & Josh




 A2M4:

 	Collision tiles:

 		These are stored as 8bpp 16x16 tiles (although treated as a 1bpp array)

 		For each pixel:
 			00 - Air
 			01 - Solid ground

 		Entirely empty or solid tiles (with tile indexes of 00 and 01) are generated at runtime.


 	Debug menu:

 		- The debug strings are stored in plain text, as opposed to the internal encoding seen in the dialog text. These are the known strings:
 			> Level
 			> MapX
 			> MapY
 			> FX Player
 			> Music Player
 			> Obj Viewer
 			> Asset Viewer

 		- The debug menu code is present in the game's ROM, but no remaining code seems to call the relevant functions.


 	Sound engine:

 		- All of the above games use Shin'en's GAX Sound Engine for their audio mixing. The only games that don't use this engine also don't use Stéphane's game engine (i.e High School Musical). Refer to the GAX documents for a more thorough overview of how it works (to do).

 			For example, in Chicken Little, the data is stored like this, directly after the debug menu strings:
 			u32[*] - Pointers to each subsong

 			(These have been observed to be in any order. One example of this is Monster House)
 			GAX_Blob - Music data (music.o)
 			GAX_Blob - SFX data (fx.o)

 			To-do: 
 				- Where is the FX pointer?
 				- Chicken Little's FX mapping differs from the internal FX mapping in the blob.


 	Save RAM:
 		- The save data format is highly customizable, and allows up to 3 save slots at a time. The smallest save size I have seen is in Chicken Little (0xA0 bytes), while the largest is Monster House (0xF7 bytes).

 		- Before every save file is a 16-byte header, which is also used for checking the integrity of all of the saves on the SRAM chip (for detecting corruption or intentional tampering):

 			- u16 - Checksum
 			- u16 - ??
 			- u32 - ??

 			- char[4] - Game engine identifier

 			- u8 - ?? (unused?)
 			- u8 - ??
 			- u8 - ?? (unused?)
 			- u8 - ?? (unused?)


 	Passwords:
 		Only spotted in Drake & Josh so far.
 		In that game, the password is composed of 4 entries,
 		with 8 icons each.

 		To do: everything else


 	Dialogue system:

 		Text data:

 			u16 - Global font index

 				This is the font to use for the entire text stream.

 				For example, Chicken Little uses these values for its fonts:
 					> 0x0000 - Font (Menus)
 					> 0x0100 - Font (Cutscenes)
 					> 0x0300 - Alien characters

 			u16 - Global palette index

 			u16 - Unused (always set to 0)

 			u16 - Portrait index
 				> This is unused in A2M games that use the talking-heads cutscene system.


 			Encoded text stream data begins here:

 				The text data is remapped in a certain way:

 					If a character is lowercase, the character is XORed by 32.

 					If a character is uppercase or is a symbol (i.e punctuation),
 					the character is incremented by 32.

 					Any special characters are remapped using a table?
 					Any special characters with a resulting value more than 0x7A
 					has a 0x80 byte appended at the start.

 					Any Japanese characters start from 0x80C0. The small characters are seperated into 80F5-80FF. 

 					> For example:
 						0x80C1 = あ
 						0x80C2 = い
 						0x80C3 = う
 						0x80C4 = え
 						0x80C5 = お
 						0x80C6 = か
 						...
 						0x80D3 = て

 					The alternate characters are 8101+.

 					> For example:
 						0x8101 = が

 					Every space is the byte string 0xFFFC.


 			u16 - 0xFFFE -> this ends the text stream.
 			This is padded with 0x00 to the nearest dword


 		Dialog data:

 			u16  - Frames to wait before executing
 			u8   - Skips command if not 0
 			u8   - Always set to 5. This is treated as a magic number, 
 				   and is checked for every dialog command. If this isn't
 				   set to 5, the command is ignored

 			u8   - Command type

 				00 -> Create text
 				01 -> Create mugshot actor
 				02 -> Hide mugshot actor
 				03 -> Create text (w/ dialog box)
 				04 -> ~~
 				05 -> End cutscene
 				06 -> ~~
 				07 -> ~~
 				0A -> Load level ID
 				0C -> Play sound ID
 				0D -> Fade out to black
 				0E -> Fade in from black
 				0F -> Stop sound ID
 				11 -> Related to screen variables
 				12 -> Related to screen variables
 				13 -> Set music update boolean
 				14 -> Play music ID


 			<Command types>


 				Create text (0x00):

 					u8 - Character ID
 					u8 - Dialog line index
 					u8 - Font offset (broken?)
 					u8 - Unused


 				Create mugshot actor (0x01):

 					u8 - Character mugshot index

 						> Any dialog that is displayed after
 						  the mugshot is loaded must have its ID
 						  match this index. If not the cutscene system 
 						  will skip past it until the bytestream is valid.

 					u8 - Mugshot direction

 						0 -> left
 						1 -> right

 					u8 - Reserved
 					u8 - Unknown (always set to 0)


 				Hide mugshot actor (0x02):

 					u8   - Character mugshot index
 					bool - Whenever or not to slide the sprite off-screen	
 						> Typically set to 0 in most cases			


 				Create textbox (0x03):

 					u8 - Character ID
 					u8 - Dialog line index
 					u8 - Font offset (broken?)

 					u8 - Dialog box style


 				?? (0x04):
 					> unknown

 				?? (0x05):

 					u8  - Reserved
 					u16 - Set to 0x2 if ending a cutscene


 				?? (0x06):
 					> unknown

 				?? (0x07):
 					> unknown


 				Load level ID (0x0A):
 					u8 - Level index

 				Play sound ID (0x0C):
 					u8 - Sound effect index to play


 				?? (0x0D):
 					> No parameters

 				?? (0x0E):
 					> No parameters


 				Stop sound ID (0x0F):
 					u8 - Sound effect index to stop

 				Related to screen variables (0x11, 0x12):
 					u8 - Unknown

 				Set music update boolean (0x13):
 					bool -> Truth value to update the boolean to

 				Play music ID (0x14)
 					u8 -> Music track index


 		Cutscene data:

 			To do: everything!

 			This is seen in games such as Monster House and The Ant Bully.
 			Use cases for this are ingame cutscenes w/ dialog boxes.

 			
 	Levels:

 		Tilemap data:

 			
 			u8 - Tile packing type bitfield

 				bit 0 -> Compress tilemap (used for screens)
 				bit 1 -> Compress tilemap (used in levels)
 				bit 2 -> ~~
 				bit 7 -> ~~ (Always set?)

 			u8 - Tile-related

 				00 -> Shifts tilemap to the right slightly
 				01 -> ~~
 				02:FF -> Tile 0 with palette 0 across the screen


 			u8  - Tile width
 			u8  - Tile height

 			u16 - Map width
 			u16 - Map height
 				> If the map width/height is less than what it's
 				  designed for, The display width/height is modulo'd by this number


 			u8 - Tilemap properties

 				bit 0:1 -> Priority index (0 to 3)
 				bit 2:3 -> Tileset index
 				bit 4:6 -> Unused
 				bit 7   -> 8bpp mode

 			u8 - Unknown
 			u8 - Tile data read offset

 			u8 - Reserved


 			If packing bit 1 is set:

 				u32 - Tilemap address (not ROM address)
 					> Calculated and displayed correctly if the address is word-aligned
 				
 				<Unused here>
 					> u16  - Height in pixels
 					> u8 - Unused
 					> u8  - Width in pixels

 				u32 - Mostly (if not always) set to 0x00000000

 				u8 - ~~ (Decoding bitfield?)
 				u8 - ~~
 				u8 - ~~
 				


 				<Tilemap data (Compressed)>

 					u8 - Number of commands to decode
 					u8 - Uncompressed size in bytes?

 					- The non compressed entries are just u8 indexes into the metatile data
 					- Compression is unknown (pretty unintuitive as to how it works)

 					> Padded to nearest dword


 			If not:

 				u32 - Tilemap address (not ROM address)
 					> Calculated and displayed correctly if the address is word-aligned
 				
 				<Unused here>
 					> u16  - Height in pixels
 					> u8 - Unused
 					> u8  - Width in pixels

 				u32 - Mostly (if not always) set to 0x00000000

 				u8[*] - Tile index
 					> Number of indexes is calculated using:
 						map width * map height	



 			Metatile definition data:


 				u16 - Subtile properties

 					->  YYYYXXXXXXXXXXXX
 						bits 0-11  -> tile ID
 						bits 12-15 -> palette ID

 				For example: if a 16x16 metatile rule is described, a single metatile takes up a single dword, and is formatted like this:

 					[A] [B]

 					[C] [D] ...

 				The tiles are stored in ascending, rightwards order here.


 				If the header declares absolute tile indexing:

 					u8 - Palette index (0x00-0x3F)
 						The resulting index into the palette RAM is calculated as is:
 						> (a & 0x40) / 4

 					u8 - Reserved

 					u16 - Absolute index into tile data




 		Collision map:

 			The collision data is stored as an 8bpp bitmap array. Each entry is an entry in the level's collision map. Each entry is also represented in-game as a 16x16 collision block. The size of the data is the W tile count * the H tile count.

 			For example: These are the values that Chicken Little uses:

 				0x00 -> nothing
 				0x01 -> ground tile

 				0x2c -> jump thru solid (left)
 				0x30 -> jump thru solid
 				0x2e -> jump thru solid (right)

 				0x37 -> bouncy tile

 				0x58, 0x50 -> climbable tile (not solid)
 				0x2c, 0x30 -> climbable tile (solid)


 		Object list (WIP):

 			To do: Where are the positions stored, and how?

 			Object property chunk (WIP):
 				...
 				u16 -> Object type
 				u16 -> Object params / state value

 				u16[2] -> set to 0xFFFF if not in use, unknown purpose

 				u16 -> Object ID (read by the game, but not used)
 				u16 -> ?
 				u16 -> ?

 				u16 -> Count of objects


 				...



 		Footer (WIP):


 			Unknown data[*]:
 				s16 - X
 				s16 - Y
 				u16 - Unused
 				u16 - Packet ID


 			Unknown pointers:
 				u32*[*] - ~~
 			

 			Layer setting[*]:
 				u8 - Tilemap ID 

 				u8 - Bitfield(?)
 				   -> bit 0 - Disable horizontal scrolling
 				   -> bit 1 - Disable all scrolling
 				   -> bit 3 - Enable constant scrolling

 				u16 - Reserved

 				s16 - Param #1
 				s16 - Param #2


 			char[16] -> Level name (i.e School01a, Logo_A2M, etc.)
 			-> padded with 0x00

 			<8 bytes, this depends on size>
 			u16 - Global scanline effect params
 			u16 - ~~

 			bool - Use absolute tile indexing
 			bool - ~~
 			u16  - ~~
 			u16  - Layer count
 			u16  - Reserved

 			u32 - ~~
 			u32 - ~~
 			u32 - ~~
 			u16 - ~~

 			u16 - Tileset index
 			u16 - Tileset-related (unknown)
 			u16 - Palette index

 			u32 - Reserved

 			u32  - ~~
 			u32  - ~~
 			u32* - ~~
 			u32  - ~~

 			u16 - Pointer list width
 			u16 - Pointer list height
 			u32 - Pointer list address (relative)

 			u32* - ~~

 			u32    - Layer setting data start offset
 				-> In Chicken Little, the offset is calculated by adding this offset to the ROM address 0x81D8474

 			u32[2] - ~~
 			u32    - Unused
 			u32*   - ~~




 	Character controller (WIP):

 		> Notes:
 			- In Chicken Little, there is a u32 constant for velocity changes, which is treated as if it were a float.
 				- These are the max velocity speed for specific movement actions, like moving in-air, moving left or right, moving then jumping, etc.

 			- Collision tiles are interacted with per-pixel.

 			- Some games use fixed point 16.16 floats for positions[3].


 	Palettes:

 		Stored in the general GBA color format, but the first color of each row is black instead of pink/magenta. This doesn't matter as that color is simply ignored.


 	Objects / animations:

 		Palettes seem to be not a part of this data, and are called seperately.
 		This allows for calling of the same object with different display properties (i.e transparent tutorial player NPCs like those seen in Chicken Little or Kim Possible 2)


 		<Unknown data>

 		Sprite graphic data:
 			- Stored in 4bpp or 8bpp little-endian tiles (8x8 px per tile).
 			- This stores every tile of an animation frame
 			- This is padded with 0x00 to the nearest dword

 		Animation data:

 			Keyframe:

 				u16 - Keyframe chunk size
 				u32 - Sprite graphic data offset
 					> Seems to be different for every frame. This suggests that
 					this is remapping the graphics data onto every subsprite.
 					> This is also not a ROM address, which implies there is
 					some offset calculation going on to convert it into a ROM pointer

 				u16 - ?

 				Sprite placement:
 					s16 - Sprite offset (X)
 					s16 - Sprite offset (Y)


 				u16[2] - ?

 				u8 - Subsprite count
 					> Number of sprites in a given animation frame.
 					> Maximum is ~97 sprites
 				s8 - Frame speed
 				u8 - Frame ID

 				bool (u8) - Is a sound playing back on this keyframe?
 				u8 - ?
 				u8 - Known values are 8 and 0


 				Subsprite placement:

 					For each subsprite:

 						s8 - Subsprite Y position

 						u8 - Subsprite properties #1

 							bit 0 - Transform
 							bit 1 - Visibility
 							bit 2 - Blend effect
 							bit 3 - Window
 							bit 4 - Mosaic

 							bit 5 - Bit depth
 								0 -> 4bpp
 								1 -> 8bpp


 							bit 6 - Double/halve tile height 
 							(i.e 8x8 -> 8x16, 32x32 -> 32x16)

 							bit 7 - Double/halve tile width  
 							(i.e 8x8 -> 16x8, 32x32 -> 16x32)

 								> Note: When both bits 6 and 7
 								  are set, they don't do anything


 						u8 - Subsprite X position

 						u8 - Subsprite properties #2

 							bit 0 - Off-screen(?)
 							bit 1 - *unused*
 							bit 2 - *unused*
 							bit 3 - *unused*

 							bit 4 - Horizontal mirror
 							bit 5 - Vertical mirror

 							bit 6-7 - Tile multiplier
 								0 - 8x8
 								1 - 16x16
 								2 - 32x32
 								3 - 64x64

 				~
 				If a sound is defined:
 					u8 - Set to 0x02
 					u8 - If this is more than 0x0 there is no sound
 					u16 - SFX index
 						> In Chicken Little, this uses a different
 						SFX mapping than observed in the original GAX FX blob.

 						Check me: This and the sound effect player menu rely on a
 						remapping of the GAX sound effect bank. Is this
 						done in just Chicken Little or does this occur in
 						other games as well?

 				If not, then:
 					u16 - ?? (seems to depend on the subsprite count over every frame of the animation?)
 				~

 		u16 - Object script (for every frame)
 		u16 - *unused*
 		u16 - Palette offset
 		u16 - Object script (on init)
 		u8  - Interactibility with objects?
 			> in Chicken Little, 0x3 means that the object can interact with acorns

 		u8  - Animation count
 		u8  - Number of animations to fetch on init
 		u8  - Starting animation index offset

 		<For each animation>
 			u32 - Relative pointer to animation data
 			u8  - Animation index
 			u8  - ??
 			u32 - Pointer to script (on animation init?)
 			u16 - ??


 Notes:
 	> The A2Mx Game Engine did not debut on Ice Age for the GBA. The engine used in that game was instead done by Vincent Van Eeckhout, with the tools developed by Simon Chouinard. Stéphane's game engine actually debuted in 2003 on Scooby-Doo!: Mystery Mayhem for the same system.


 [1] - https://www.mobygames.com/game/159188/ed-edd-n-eddy-the-mis-edventures/credits/gameboy-advance/
 [2] - https://www.mobygames.com/game/205630/disneys-chicken-little/credits/gameboy-advance/
 [3] - https://tasvideos.org/Forum/Topics/17310
	A2Mx Game Engine
	> The A2Mx game engine is a 2D engine that has been used for platformer, isometric and top-down games, with support for SRAM saving (or passwords), and cutscenes. It was developed by Stéphane Hockenhull[1] (https://rv6502.ca/), with the tools being developed by Benoit Hubert[2].
	> A2Mx is not the confirmed name of the engine, but it could be judging by the names "A2M4" and so on appearing in the ROM.


	> Known games

	A2M0:
	- Enchanted - Once Upon Andalasia (last game)

	A2M1:
	- Kim Possible 2: Drakken's Demise
	- Happy Feet
	- everGirl
	- Scooby-Doo: Mystery Mayhem (debut)

	A2M2:
	- Lizzie McGuire 2 - Lizzie Diaries

	A2M4:
	- Chicken Little

	A2M5:
	- Ed Edd & Eddy: The Mis-Ed-Ventures

	A2M7:
	- The Sims 2: Pets

	A2MR:
	- Monster House

	A2MT:
	- Drake & Josh




	A2M4:

	Collision tiles:

	These are stored as 8bpp 16x16 tiles (although treated as a 1bpp array)

	For each pixel:
	00 - Air
	01 - Solid ground

	Entirely empty or solid tiles (with tile indexes of 00 and 01) are generated at runtime.


	Debug menu:

	- The debug strings are stored in plain text, as opposed to the internal encoding seen in the dialog text. These are the known strings:
	> Level
	> MapX
	> MapY
	> FX Player
	> Music Player
	> Obj Viewer
	> Asset Viewer

	- The debug menu code is present in the game's ROM, but no remaining code seems to call the relevant functions.


	Sound engine:

	- All of the above games use Shin'en's GAX Sound Engine for their audio mixing. The only games that don't use this engine also don't use Stéphane's game engine (i.e High School Musical). Refer to the GAX documents for a more thorough overview of how it works (to do).

	For example, in Chicken Little, the data is stored like this, directly after the debug menu strings:
	u32[*] - Pointers to each subsong

	(These have been observed to be in any order. One example of this is Monster House)
	GAX_Blob - Music data (music.o)
	GAX_Blob - SFX data (fx.o)

	To-do:
	- Where is the FX pointer?
	- Chicken Little's FX mapping differs from the internal FX mapping in the blob.


	Save RAM:
	- The save data format is highly customizable, and allows up to 3 save slots at a time. The smallest save size I have seen is in Chicken Little (0xA0 bytes), while the largest is Monster House (0xF7 bytes).

	- Before every save file is a 16-byte header, which is also used for checking the integrity of all of the saves on the SRAM chip (for detecting corruption or intentional tampering):

	- u16 - Checksum
	- u16 - ??
	- u32 - ??

	- char[4] - Game engine identifier

	- u8 - ?? (unused?)
	- u8 - ??
	- u8 - ?? (unused?)
	- u8 - ?? (unused?)


	Passwords:
	Only spotted in Drake & Josh so far.
	In that game, the password is composed of 4 entries,
	with 8 icons each.

	To do: everything else


	Dialogue system:

	Text data:

	u16 - Global font index

	This is the font to use for the entire text stream.

	For example, Chicken Little uses these values for its fonts:
	> 0x0000 - Font (Menus)
	> 0x0100 - Font (Cutscenes)
	> 0x0300 - Alien characters

	u16 - Global palette index

	u16 - Unused (always set to 0)

	u16 - Portrait index
	> This is unused in A2M games that use the talking-heads cutscene system.


	Encoded text stream data begins here:

	The text data is remapped in a certain way:

	If a character is lowercase, the character is XORed by 32.

	If a character is uppercase or is a symbol (i.e punctuation),
	the character is incremented by 32.

	Any special characters are remapped using a table?
	Any special characters with a resulting value more than 0x7A
	has a 0x80 byte appended at the start.

	Any Japanese characters start from 0x80C0. The small characters are seperated into 80F5-80FF.

	> For example:
	0x80C1 = あ
	0x80C2 = い
	0x80C3 = う
	0x80C4 = え
	0x80C5 = お
	0x80C6 = か
	...
	0x80D3 = て

	The alternate characters are 8101+.

	> For example:
	0x8101 = が

	Every space is the byte string 0xFFFC.


	u16 - 0xFFFE -> this ends the text stream.
	This is padded with 0x00 to the nearest dword


	Dialog data:

	u16 - Frames to wait before executing
	u8 - Skips command if not 0
	u8 - Always set to 5. This is treated as a magic number,
	and is checked for every dialog command. If this isn't
	set to 5, the command is ignored

	u8 - Command type

	00 -> Create text
	01 -> Create mugshot actor
	02 -> Hide mugshot actor
	03 -> Create text (w/ dialog box)
	04 -> ~~
	05 -> End cutscene
	06 -> ~~
	07 -> ~~
	0A -> Load level ID
	0C -> Play sound ID
	0D -> Fade out to black
	0E -> Fade in from black
	0F -> Stop sound ID
	11 -> Related to screen variables
	12 -> Related to screen variables
	13 -> Set music update boolean
	14 -> Play music ID


	<Command types>


	Create text (0x00):

	u8 - Character ID
	u8 - Dialog line index
	u8 - Font offset (broken?)
	u8 - Unused


	Create mugshot actor (0x01):

	u8 - Character mugshot index

	> Any dialog that is displayed after
	the mugshot is loaded must have its ID
	match this index. If not the cutscene system
	will skip past it until the bytestream is valid.

	u8 - Mugshot direction

	0 -> left
	1 -> right

	u8 - Reserved
	u8 - Unknown (always set to 0)


	Hide mugshot actor (0x02):

	u8 - Character mugshot index
	bool - Whenever or not to slide the sprite off-screen
	> Typically set to 0 in most cases


	Create textbox (0x03):

	u8 - Character ID
	u8 - Dialog line index
	u8 - Font offset (broken?)

	u8 - Dialog box style


	?? (0x04):
	> unknown

	?? (0x05):

	u8 - Reserved
	u16 - Set to 0x2 if ending a cutscene


	?? (0x06):
	> unknown

	?? (0x07):
	> unknown


	Load level ID (0x0A):
	u8 - Level index

	Play sound ID (0x0C):
	u8 - Sound effect index to play


	?? (0x0D):
	> No parameters

	?? (0x0E):
	> No parameters


	Stop sound ID (0x0F):
	u8 - Sound effect index to stop

	Related to screen variables (0x11, 0x12):
	u8 - Unknown

	Set music update boolean (0x13):
	bool -> Truth value to update the boolean to

	Play music ID (0x14)
	u8 -> Music track index


	Cutscene data:

	To do: everything!

	This is seen in games such as Monster House and The Ant Bully.
	Use cases for this are ingame cutscenes w/ dialog boxes.


	Levels:

	Tilemap data:


	u8 - Tile packing type bitfield

	bit 0 -> Compress tilemap (used for screens)
	bit 1 -> Compress tilemap (used in levels)
	bit 2 -> ~~
	bit 7 -> ~~ (Always set?)

	u8 - Tile-related

	00 -> Shifts tilemap to the right slightly
	01 -> ~~
	02:FF -> Tile 0 with palette 0 across the screen


	u8 - Tile width
	u8 - Tile height

	u16 - Map width
	u16 - Map height
	> If the map width/height is less than what it's
	designed for, The display width/height is modulo'd by this number


	u8 - Tilemap properties

	bit 0:1 -> Priority index (0 to 3)
	bit 2:3 -> Tileset index
	bit 4:6 -> Unused
	bit 7 -> 8bpp mode

	u8 - Unknown
	u8 - Tile data read offset

	u8 - Reserved


	If packing bit 1 is set:

	u32 - Tilemap address (not ROM address)
	> Calculated and displayed correctly if the address is word-aligned

	<Unused here>
	> u16 - Height in pixels
	> u8 - Unused
	> u8 - Width in pixels

	u32 - Mostly (if not always) set to 0x00000000

	u8 - ~~ (Decoding bitfield?)
	u8 - ~~
	u8 - ~~



	<Tilemap data (Compressed)>

	u8 - Number of commands to decode
	u8 - Uncompressed size in bytes?

	- The non compressed entries are just u8 indexes into the metatile data
	- Compression is unknown (pretty unintuitive as to how it works)

	> Padded to nearest dword


	If not:

	u32 - Tilemap address (not ROM address)
	> Calculated and displayed correctly if the address is word-aligned

	<Unused here>
	> u16 - Height in pixels
	> u8 - Unused
	> u8 - Width in pixels

	u32 - Mostly (if not always) set to 0x00000000

	u8[*] - Tile index
	> Number of indexes is calculated using:
	map width * map height



	Metatile definition data:


	u16 - Subtile properties

	-> YYYYXXXXXXXXXXXX
	bits 0-11 -> tile ID
	bits 12-15 -> palette ID

	For example: if a 16x16 metatile rule is described, a single metatile takes up a single dword, and is formatted like this:

	[A] [B]

	[C] [D] ...

	The tiles are stored in ascending, rightwards order here.


	If the header declares absolute tile indexing:

	u8 - Palette index (0x00-0x3F)
	The resulting index into the palette RAM is calculated as is:
	> (a & 0x40) / 4

	u8 - Reserved

	u16 - Absolute index into tile data




	Collision map:

	The collision data is stored as an 8bpp bitmap array. Each entry is an entry in the level's collision map. Each entry is also represented in-game as a 16x16 collision block. The size of the data is the W tile count * the H tile count.

	For example: These are the values that Chicken Little uses:

	0x00 -> nothing
	0x01 -> ground tile

	0x2c -> jump thru solid (left)
	0x30 -> jump thru solid
	0x2e -> jump thru solid (right)

	0x37 -> bouncy tile

	0x58, 0x50 -> climbable tile (not solid)
	0x2c, 0x30 -> climbable tile (solid)


	Object list (WIP):

	To do: Where are the positions stored, and how?

	Object property chunk (WIP):
	...
	u16 -> Object type
	u16 -> Object params / state value

	u16[2] -> set to 0xFFFF if not in use, unknown purpose

	u16 -> Object ID (read by the game, but not used)
	u16 -> ?
	u16 -> ?

	u16 -> Count of objects


	...



	Footer (WIP):


	Unknown data[*]:
	s16 - X
	s16 - Y
	u16 - Unused
	u16 - Packet ID


	Unknown pointers:
	u32[] - ~~


	Layer setting[*]:
	u8 - Tilemap ID

	u8 - Bitfield(?)
	-> bit 0 - Disable horizontal scrolling
	-> bit 1 - Disable all scrolling
	-> bit 3 - Enable constant scrolling

	u16 - Reserved

	s16 - Param #1
	s16 - Param #2


	char[16] -> Level name (i.e School01a, Logo_A2M, etc.)
	-> padded with 0x00

	<8 bytes, this depends on size>
	u16 - Global scanline effect params
	u16 - ~~

	bool - Use absolute tile indexing
	bool - ~~
	u16 - ~~
	u16 - Layer count
	u16 - Reserved

	u32 - ~~
	u32 - ~~
	u32 - ~~
	u16 - ~~

	u16 - Tileset index
	u16 - Tileset-related (unknown)
	u16 - Palette index

	u32 - Reserved

	u32 - ~~
	u32 - ~~
	u32* - ~~
	u32 - ~~

	u16 - Pointer list width
	u16 - Pointer list height
	u32 - Pointer list address (relative)

	u32* - ~~

	u32 - Layer setting data start offset
	-> In Chicken Little, the offset is calculated by adding this offset to the ROM address 0x81D8474

	u32[2] - ~~
	u32 - Unused
	u32* - ~~




	Character controller (WIP):

	> Notes:
	- In Chicken Little, there is a u32 constant for velocity changes, which is treated as if it were a float.
	- These are the max velocity speed for specific movement actions, like moving in-air, moving left or right, moving then jumping, etc.

	- Collision tiles are interacted with per-pixel.

	- Some games use fixed point 16.16 floats for positions[3].


	Palettes:

	Stored in the general GBA color format, but the first color of each row is black instead of pink/magenta. This doesn't matter as that color is simply ignored.


	Objects / animations:

	Palettes seem to be not a part of this data, and are called seperately.
	This allows for calling of the same object with different display properties (i.e transparent tutorial player NPCs like those seen in Chicken Little or Kim Possible 2)


	<Unknown data>

	Sprite graphic data:
	- Stored in 4bpp or 8bpp little-endian tiles (8x8 px per tile).
	- This stores every tile of an animation frame
	- This is padded with 0x00 to the nearest dword

	Animation data:

	Keyframe:

	u16 - Keyframe chunk size
	u32 - Sprite graphic data offset
	> Seems to be different for every frame. This suggests that
	this is remapping the graphics data onto every subsprite.
	> This is also not a ROM address, which implies there is
	some offset calculation going on to convert it into a ROM pointer

	u16 - ?

	Sprite placement:
	s16 - Sprite offset (X)
	s16 - Sprite offset (Y)


	u16[2] - ?

	u8 - Subsprite count
	> Number of sprites in a given animation frame.
	> Maximum is ~97 sprites
	s8 - Frame speed
	u8 - Frame ID

	bool (u8) - Is a sound playing back on this keyframe?
	u8 - ?
	u8 - Known values are 8 and 0


	Subsprite placement:

	For each subsprite:

	s8 - Subsprite Y position

	u8 - Subsprite properties #1

	bit 0 - Transform
	bit 1 - Visibility
	bit 2 - Blend effect
	bit 3 - Window
	bit 4 - Mosaic

	bit 5 - Bit depth
	0 -> 4bpp
	1 -> 8bpp


	bit 6 - Double/halve tile height
	(i.e 8x8 -> 8x16, 32x32 -> 32x16)

	bit 7 - Double/halve tile width
	(i.e 8x8 -> 16x8, 32x32 -> 16x32)

	> Note: When both bits 6 and 7
	are set, they don't do anything


	u8 - Subsprite X position

	u8 - Subsprite properties #2

	bit 0 - Off-screen(?)
	bit 1 - unused
	bit 2 - unused
	bit 3 - unused

	bit 4 - Horizontal mirror
	bit 5 - Vertical mirror

	bit 6-7 - Tile multiplier
	0 - 8x8
	1 - 16x16
	2 - 32x32
	3 - 64x64

	~
	If a sound is defined:
	u8 - Set to 0x02
	u8 - If this is more than 0x0 there is no sound
	u16 - SFX index
	> In Chicken Little, this uses a different
	SFX mapping than observed in the original GAX FX blob.

	Check me: This and the sound effect player menu rely on a
	remapping of the GAX sound effect bank. Is this
	done in just Chicken Little or does this occur in
	other games as well?

	If not, then:
	u16 - ?? (seems to depend on the subsprite count over every frame of the animation?)
	~

	u16 - Object script (for every frame)
	u16 - unused
	u16 - Palette offset
	u16 - Object script (on init)
	u8 - Interactibility with objects?
	> in Chicken Little, 0x3 means that the object can interact with acorns

	u8 - Animation count
	u8 - Number of animations to fetch on init
	u8 - Starting animation index offset

	<For each animation>
	u32 - Relative pointer to animation data
	u8 - Animation index
	u8 - ??
	u32 - Pointer to script (on animation init?)
	u16 - ??


	Notes:
	> The A2Mx Game Engine did not debut on Ice Age for the GBA. The engine used in that game was instead done by Vincent Van Eeckhout, with the tools developed by Simon Chouinard. Stéphane's game engine actually debuted in 2003 on Scooby-Doo!: Mystery Mayhem for the same system.


	[1] - https://www.mobygames.com/game/159188/ed-edd-n-eddy-the-mis-edventures/credits/gameboy-advance/
	[2] - https://www.mobygames.com/game/205630/disneys-chicken-little/credits/gameboy-advance/
	[3] - https://tasvideos.org/Forum/Topics/17310