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AI Game Decompilation: A Deep Dive

Undocumented Behavior

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Decompilation and reverse engineering turn a game's machine code back into source code people can read. For thirty years, fans have done it by hand, one function at a time, until their code compiles into the exact same bytes as the cartridge. Over the past year, AI agents started doing it too, and one of them got caught cheating.

It's a test with an answer key, and the answer key is the game. From Super Mario 64 to Snowboard Kids 2, here's how matching decompilation works, what AI changed, what it tried to cheat on, and what still needs people.

Chapters:
0:00 Cold open
0:40 A sealed box
1:50 The answer key
3:40 Shortcuts
4:45 A puzzle machines love
6:02 Teaching to the test
7:29 What still needs people
8:45 What players get

Which game should be next? Tell me in the comments.

This video doesn't link to any download. Decompilations and recompilations ship no game files: you need your own copy of the game.

ABOUT THE CODE ON SCREEN
• Every Super Mario 64 listing (Mario's jump, act_jump) is real compiler output: the n64decomp/sm64 source compiled with IDO 5.3 (decompals' static recompilation) and the US flags, for this video. The three "guesses" are ours; their bytes and diffs are what that compiler produced.
• The Snowboard Kids 2 checksum commit (34513be, 5 Dec 2025), Chris Lewis's fix (5dcf8a9, 14 Dec 2025), the hooks, notes, renames and the title-screen cheat routine are from the public cdlewis/snowboardkids2-decomp and cdlewis/snowboardkids-decomp repositories.
• Marked "illustration": the memory search, the permuter shuffle, the routine-replacement grid, the agent queue, and act_jump rendered in N64: Recompiled's output style.

SOURCES
• Chris Lewis, blog.chrislewis.au: "The Unexpected Effectiveness of One-Shot Decompilation with Claude" (Nov 2025), "The Long Tail of LLM-Assisted Decompilation" (Feb 2026), "Snowboard Kids 2 is 100% Decompiled" (May 2026), "Decompiling a Nintendo 64 Game in 84 Days" (Aug 2026), "Introducing Snowboard Kids: Recompiled" (Oct 2026)
• Maurice Heumann, momo5502.com: "500+ Billion Tokens Later: Letting AI Agents Decompile A First-Person Shooter" (9 Oct 2026)
• Kyle Orland, Ars Technica: "Beyond emulation: The massive effort to reverse-engineer N64 source code" (May 2020)
• decomp.dev progress histories: Snowboard Kids, Snowboard Kids 2, Super Smash Bros. Melee
• n64decomp/sm64 (Makefile, source), pret/pokered (engine/battle/core.asm), diasurgical/devilution, OpenRCT2 v0.0.5 release notes (27 Dec 2016), N64Recomp/N64Recomp README, decompals/ido-static-recomp
• Lewis Galoob Toys, Inc. v. Nintendo of America, Inc., 964 F.2d 965 (9th Cir. 1992)
• FRVR: Zelda and Banjo Recompiled dev on "slopcomps" (Darío; RPCS3 statement)
• Ship of Harkinian changelog (text-to-speech)
• SubmitGame/awesome-decomp-games (1,432 projects, 1,220 games, 11 Oct 2026)
• GameShark code for Super Mario 64 (US) infinite lives: 8033B21D 0064 (community code lists)

FOOTAGE (muted; all credit to the uploaders)
• RetroGame.Stream: Super Mario 64 - N64 - Full Playthrough No Commentary
• Duif: Super Mario 64 - PC Port Gameplay [No Commentary]
• LongplayArchive: Longplay of Snowboard Kids
• Video Game Galaxy: Snowboard Kids 2 Longplay - 1080p
• M0d3rn R3tr0 Gam3r: Snowboard Kids 2 N64 Recomp Full Playthrough
• Game Genie TV commercial (1990, Lewis Galoob Toys)
• Nintendo Utopia: Pokemon Red for Game Boy HD Full Playthrough
• Darío: Super Mario 64 Ray Tracing (sm64rt) - Technical Preview Trailer
• Kaze Emanuar: Return to Yoshi's Island 64 Demo Release
• SourceSpy91: The Legend Of Zelda: Ocarina Of Time - Full Game - No Commentary
• GameHive: Diablo (DevilutionX) Full Playthrough
• Azungu: RollerCoaster Tycoon 2 - Crazy Castle (No Commentary Longplay)
• Wiseguy: Zelda 64: Recompiled for PC - Majora's Mask Release Trailer; Banjo: Recompiled Release Trailer
• Skyth: Unleashed Recompiled - Release Trailer
• World of Longplays: GameCube Longplay [002] Super Smash Bros. Melee
• Matty: Ship of Harkinian v2.0, 60 fps ultrawide
• Photo: SGI Indy, Peter Wallén, CC BY 3.0 (Wikimedia Commons)
• Screenshots and images: Chris Lewis (blog.chrislewis.au); Snowboard Kids: Recompiled launcher art by M. Lee Lunsford

#decompilation #reverseengineering #N64

20 Comments

@UndocumentedBehavior Creator 11 hours ago (edited) Pinned

This is my first deep dive like this, and it took a lot of digging: commit histories and compiling Mario 64's actual code so the bytes on screen are real. Every source is in the description.

If you work on a decomp or a recomp and I got something wrong, please tell me below.

Since it's my first one, I'd love honest feedback: what worked, and where did it drag? And if you'd watch more, which deep dive should I do next?

Clarification from @striderskorpion: the GameShark writes values into RAM, as shown in the video, but the Game Genie worked differently. It intercepted the game's reads from the cartridge ROM and swapped in new values.

@andrewdunbar828 7 hours ago

It's been called "reverse engineering" since decades before Nintendo made their first console.

@femiairboy94 11 hours ago

Hey man just wanted to say, keep it up. Your videos are amazing and they have a therapeutic nature to them. You will definitely blow up soon.

@revcmods 5 hours ago

3:43 this is what happened with the reverse engineered gta3 and vice city projects (re3/reVC). So almost all the function and variable names are the real ones written by rockstar in the early 2000s. The reverse engineering team said they wouldn’t have been able to finish as quickly without the debug symbols.

@spurce2179 1 hour ago

Thank you for being the person who finally delivered the perspective into what happened without doom trolling.
This makes sense and its understandable. Fantastic work

@thelenbax8497 7 hours ago

Rayman 2 on the Dreamcast, Shadow of the Colossus for the PS2 and Gravity Rush 2 would be phenomenal. Your machine code and source code explanation was so well condensed, great job 👌

@akshatbhardwaj 10 hours ago (edited)

Hey man, absolutely loved your video.
I just recently started watching the videos you've uploaded. It sure seems like a lot of effort and passion have gone into making these videos. Also, your voice/video has some sort of serenity to it.

Your videos are sure to blow up soon. Keep up! Looking forward to the next one.

@Frosthorne 3 hours ago

This was a great watch! As a software engineer I definitely have mixed feelings on the advent of AI coding agents. On one hand, it's a really powerful tool when used correctly and the developer has the knowledge to steer it in the right direction or correct the code its writing. On the other, it can lead to hastily written and as you mentioned often incorrect code. I've seen some decomps where the developer actually does understand the game's internals and the source platform's architecture and merely uses the agents to speed up the process and those don't bother me as much because there's still some level of thought and care put into it.

@1kingv 6 hours ago

I really like how this video has been set up bro!

@TsiAileron 6 hours ago

Maybe we can finally get a modern release of Panzer Dragoon Saga now :)

@uolamer 2 hours ago

The Game Genie (not game shark) actually modified the assembly by intercepting the reads of the ROM. You would often do the same first steps as you would with a game shark, but then the next step would be find the assembly writing to that address and modify it to say not lower your lives.

@dwfitz 10 hours ago

Youre working day and night youll blow up soon!

@freonsp 3 hours ago

idk how no one has done it but they need to integrate JEV in the workflow as a critic agent to see the probability of the agent's commands being outside the scope or cheating from the prompt

@maxlhetvxhywxvxbm7645 11 hours ago

A game that should be decompiled next is Ghost in the Shell Stand Alone Complex on the PS2. It's over 20 years old, was never ported outside the PS2 (unless you count the PSP version) and I don't know if the game is technically considered abandonware or not, I just want the game natively on PC with widescreen, 60 FPS, mouse look, local split screen, original Japanese dub option included and maybe a functioning online multiplayer. I've searched if there is a decompilation team doing GITS but I couldn't find any, if there was I would want them to finish it manually if there against using AI tools like the Ocarina decomp team. as much as I mostly dislike AI, it is capable of preserving so much old games.

@MainGoldDragon 1 hour ago

amazing video! so much insight on how all of this works and how its not a magic 1 button press!

but where's my Ape Escape 😭😭😭

@lualdiz 7 hours ago

Goated video, all of it.

@2psah 9 hours ago

Yeah, just like others are saying. Great channel, great progress, good voice & good content. Keep it up.💯

@striderskorpion 6 hours ago

GameShark/(Pro) Action Replay and Codebreaker/Xploder work differently than the Game Genie. They write values to the RAM, while the Game Genie intercepted reads to ROM addresses. Later versions of the Pro Action Replay on the Genesis/Mega Drive and SNES did add the ability to affect RIM reads, but all other versions were RAM only.