This patch completely converts the game from using the dated stripped down Jaguar Doom engine and instead switches it to a new homebrew port based on doomhack's PrBoom port to the GBA.
Meaning, higher quality sounds, full non-simplified PC Doom maps, better framerate (yes!), graphics and music (far better music, they play in the correct level now!)

The HUD has been changed to match the one from the GBA Doom II PC Conversion pack.
Unfortunately this homebrew port doesn't contain multiplayer.

Patch the original retail GBA Doom rom with Lunar IPS and this GBADoom-PC.ips

Cheats:

Chainsaw: L, UP, UP, LEFT, L, SELECT, SELECT, UP
God mode: UP, UP, DOWN, DOWN, LEFT, LEFT, RIGHT, RIGHT
Ammo & Keys: L, LEFT, R, RIGHT, SELECT,UP, SELECT, UP
Ammo: R, R, SELECT,R, SELECT,UP, UP, LEFT
No Clipping: UP, DOWN, LEFT, RIGHT, UP, DOWN, LEFT, RIGHT
Invincibility: A, B, L, R, L, R, SELECT, SELECT
Berserk: B, B, R, UP, A, A, R, B
Invisibility: A, A, SELECT,B, A, SELECT, L, B
Auto-map: L, SELECT,R, B, A, R, L, UP
Lite-Amp Goggles: DOWN,LEFT, R, LEFT, R, L, L, SELECT
Exit Level: LEFT,R, LEFT, L, B, LEFT, RIGHT, A
Enemy Rockets (Goldeneye): A, B, L, R, R, L, B, A
FPS Ammo Counter: A, B, L, UP, DOWN, B, LEFT, LEFT

Controls:

Fire: B
Use / Sprint: A
Walk: D-Pad
Strafe: L & R
Automap: SELECT
Weapon up: A + R
Weapon down: A + L
Menu: Start

Changelog:
SVN 1.7
* Updated fork to match doomhack's latest build again!
  Which Includes:
  - Lower sky
  - Some minor speed and division accuracy optimisations
  - Screen Melting (backported from next-hack)
  - Link-time optimisation compiler flags
  
SVN 1.6
* Updated fork to match doomhack's latest build! About a 30% speed boost!
  Which Includes:
     - Gamma boost, always run save separately and autoload on their own instead of saving/loading them per save slot.
     - Sound volume settings now save
     - Massive tonne of CPU and RAM optimisations
     - Bugfix for Cyberdemon/Spider-mastermind not drawing on long distances
     - FPS Counter
* FPS counter can now be accessed via a cheat (see above).

SVN 1.5
* Gamma uses a slider now and has custom colour corrected palettes for front/non lit GBA systems.

SVN 1.4
* You can now back out of menus
* Fixed rockets / plasma projectiles sfx being quiet for the player
* Hurt me Plenty is the default difficulty again
* Merge doomhack main branch changes (automap optimisations)

SVN 1.3
* Merge changes from doomhack's main branch (RAM optimisations, awesome!)
* New Microsoft GS Wavetable Synth based soundtrack for Doom 1, ported by Sakitoshi
* Fixed a backpack ammo save/load bug

SVN 1.2.2
* Fixed GBA Micro compatibility issues.

SVN 1.2.1
* Fixed the ammo counter flickering when changing weapons, which got broken from my previous fix.

SVN 1.2
* Merged all changes from doomhack's new optimised build.
* Fixed a minor bug with the HUD ammo numbers

SVN 1.1
* Weapon selection order is restored to: Fist, Chainsaw, Pistol, Shotgun, Super Shotgun, Chaingun, Plasmagun, BFG 9000
* Gamma is in the options now instead of a hotkey.
* Options such as Gamma and Always Run are saved into your saved slots.
* And other bug general fixes and optimisations.

Homebrew port github pages:
https://github.com/Kippykip/GBADoom
https://github.com/doomhack/GBADoom

Special thanks to Sakitoshi on RomHacking.net for converting the PC Doom midis over to ImpulseTracker format.