Sondre Agledahl

Video game portfolio

Pokémon FireRed: Rocket Edition
Development time: 3 years (2014-present); Three beta versions currently released
Development tools: Assembly language / GBA scripting tools
Project type: Spare time solo project
Platform: Game Boy Advance
Download link: bit.ly/pkmfrrocketed

Gameplay video

Gameplay video by YouTube personality FeintAttacks highlighting the opening sections of the game.

Development details

Written in pure and simplified ARM assembly language (THUMB instruction set) in the Pokémon FireRed engine

Most of the game was written using the GameBoy Advance scripting tool XSE. XSE uses an instruction set that maps 1-to-1 to THUMB instructions for the GBA processor, but simplified (to commands like applymovement and setvar) based on community knowledge of the disassembled FireRed ROM.

Certain features I wanted to implement that were not present in the original FireRed, however, I had to write manually in THUMB assembly. The example below is a script that extracts information about the species and level of a Trainer's Pokémon, part of a larger set of scripts used to allow the player to steal Pokémon from Trainers they battle:

pokesteal.asm

.text
.align 2
.thumb
.thumb_func
 
main:
	push {r0-r7, lr}
	
	ldr r0, =(0x20386AE) @Trainer ID of last battled trainer
	ldrh r0, [r0]
	
	mov r1, #0x28
	mul r0, r0, r1
	
	ldr r2, =(0x823EAE8) @Trainer table
	add r2, r2, r0 @r2 now points to where the number of Pokémon trainer has is stored
	ldrb r3, [r2] @r3 now contains the number of Pokémon trainer has
 
	ldr r5, =(0x020370D2) @Variable 0x800F
	strh r3, [r5] @Stores number of Pokémon trainer has
	
	add r2, #0x4
	ldr r2, [r2] @r2 now contains a pointer to the Pokémon information
	add r2, #0x2 @r2 is now at level of Pkm1 
	
	ldr r0, =(0x0203F4A0) @freespace
	ldr r4, =(0x08245EE0) @Pokémon string table
	sub r5, #0x1A @moves r5 to location of var 0x8000
	
	mov r6, #0x0
	
loop:
@stores level of each of trainer's Pokémon in vars 0x8000, -2, -4, -6, -8 and -A
@stores species of each of trainer's Pokémon in vars 0x8001, -3, -5, -7, -9 and -B 
@stores pointer to each Pokémon's name in the correct multichoice option location
 
	ldrb r1, [r2]
	strh r1, [r5] @Stores level of Pkm in var
	
	add r2, #0x2 @r2 is now at species of Pkm
	ldrb r1, [r2]
	add r5, #0x2 @moves to next variable
	strh r1, [r5] @Stores species of Pkm in var
	
	mov r7, #0xB
	mul r1, r1, r7
	add r1, r1, r4 @r1 now contains pointer to Pkm's name string
	str r1, [r0] @stores pointer to Pkm's name in choice x
	
	add r6, #0x1 @increments iterative
	
	cmp r6, r3
	BEQ end @goes to end if loop has executed same amount of times as available Pokémon
	
	add r0, #0x8 @moves to location to store string of next choice
	add r2, #0x6 @moves to location of next Pkm's level
	add r5, #0x2 @moves to next variable
	b loop
	
end:
	pop {r0-r7, pc}
 
.align 2	

Screenshots

Screenshots from the game's third beta release (October 2017), demonstrating the game's core stealing mechanic, as well as the design of some of its new levels and elements of the story.