User:Crabb/GunstarSuperHeroes

a very nice GBA game. this is just some notes in case someone wants to go dig and find more unused content. once i figure out exactly something works, i'll post it to the main page.

if you find anything nice that isn't here, feel free to edit!

Memory Layout

Brief intro, GBA has 2 main areas of RAM; IWRAM (32 KB) and EWRAM (256 KB). IWRAM is faster to access than EWRAM, so most of the data there contains data that requires quick access (ex. objects & player)

Important note about data in IWRAM GSH often does some type of allocation with data in IWRAM, so don't expect data there to always be in the same location. to help with this, EWRAM often contains pointers to where data should be in IWRAM.

EWRAM

Addresses here are relative to EWRAM's start. (@ 0x02000000)

Offset	Type	Description
0x02:92C4	u32	Pointer to player's Gunstar struct.

IWRAM

Addresses here are relative to IWRAM's start. (@ 0x03000000)

Offset	Description
0x07F4	BIOS vector/interrupt handler.
0x2540	Shot/object table. (※ Offset may change.)

Gunstar Struct

the struct that contains... you! this is just a rough map of the player's struct.

Offset	Name	Type	Description
0x0072	input_table	u16[0xF0]	Contains a FIFO of the gunstar's previously pressed inputs. Each entry is a button/d-pad press.
0x016D	shottype	u8	The gunstar's current shot type.
0x017C	position	vec2.f16	Contains a 16.16 fixed-point vector of the gunstar's current position.
0x0184	velocity	vec2.f16	Gunstar's current velocity.
0x01BD	shottype_index	u8	The gunstar's shot type index. The game finds the shot type to use by reading shottype_table[shottype_index].
0x01BE	shottype_table	u8[3]	A table, with each value being the currently equipped shot type for that slot. For Red, it'd be [01 02 04], and for Blue, [03 02 04]

banter

• shot type 0 is unused, but functional. it uses the same EX attack as Red's Force, and there doesn't seem to be any known issues when using it.

Object Table

each object should occupy around 0xC0(?) bytes. most of this is just the result of poking around with RAM editors, so it may not be completely accurate.

※ contents of each object changes depending on the type, but the first 0x10 bytes seem to have the same purpose across every object.

Offset	Name	Type	Description
0x0008	type	u16	the object's type(?). for example, D1C5 == yellow's ship.
0x0010	position	vec2.f16	contains the object's 2D position.
0x0020	velocity	vec2.f16	contains the object's 2D velocity.
0x0028	time	u16	the time the object's been alive, in frames. (※ Only for Red's A shot.)