These are my notes from porting my Amiga game, which I originally built in Baghdad in 1993 in MC68000 assembly, to Godot, using Claude Fable 5 during last July holiday. It took an evening! Getting the feel right and shipping it took a few more weekends and evenings.
I spent the last few weeks analyzing what Claude did, feeding it my 33 years of memory of how I built the game, my notes and the git repos. It wrote the first draft of the article, and I edited line by line over a week. The screenshots of my 1993 map editor is the first I have run it since then. The one thing I never verified myself is the 108-byte explanation.
"Before starting everything, the model assembled the code using vasm on my Mac, and kept going till the binary is byte-identical to the binaries I had in my original game. Even after that, the there was mismatch of about 108 bytes. I originally used AsmOne which assembles into memory, and the game saved into the disk by saving that memory after running the game. So the original shipped files are a snapshot of the game that had already been running, not clean asm-one output."
Please post any questions. I am also releasing the original game for free.
gmerc a month ago
It's a completely new world. Random retro games I ported to modern webgl/webgpu in the last few months:
One of the most difficult reverse-engineering projects from that era for me was Stunt Car Racer on the C64 (also ported to DOS). It features a highly optimized 8-bit 3D graphics and physics engine. Fable was the first one that was able to generate a complete port of the game.
Now I am trying of Flight Simulator 4 and Wing Commander 1. Then maybe Frontier Elite 2. So much fun ....
p0w3n3d a month ago
Please do not hesitate to share stunts, if you can
s-macke a month ago
Stunt Car Racer from Geoff Crammond published by MicroProse, not Stunts from Distinctive Software.
gmerc a month ago
Strike Commander is in the works. I tried a few months ago and got quite far asset wise but stalled on the flight model, I will probably see how Fable 5.1 does from zero after this weeks limit reset. I imagine it will be able to get quite far.
aidenn0 a month ago
Strike Commander, a.k.a. the game that required QEMM386 to actually work. I do think it was the last game I got that came with a really nice manual though.
gilleain a month ago
Syndicate!! Actually, this one feels especially appropriate to use an LLM for.
shevy-java a month ago
Some old games have high re-playable value. Syndicate is one of them; UFO enemy unknown is another one, as is civilization or Masters of Orion 1. I can reply most of them quite fine. Populous was also quite decent but not quite replayable compared to the others mentioned IMO.
LordDefender a month ago
Red Baron! Wait, how, where, from Amiga? Tell me more please!
gmerc a month ago
https://redbaron.tooclever.org Demo, requires WebGPU - PC version but with modern upgrades (can be disabled), Opus redid the plane models and turned everything proper 3d, plus added ww1 frigates, flak searchlights, etc.
Steve16384 a month ago
This is amazing. I'm trying to get a handle on how you're doing this, but I can't seem to find anything specific. e.g., is it a case of prompting "Please recreate Populous for the web"?
gmerc a month ago
This post has the actual prompt used for one of my ports and the stack, and there's more info below it under "further reading".
There's really nothing much to it, all the knowledge needed is in the weights of the model, so regardless of what you want to do, you can ask "if I wanted to do this, what would be the best way / best practices to get there with my machine"
1. For each topic, write a result Markdown file in `spec/`.
2. Identify the file formats.
3. Reverse Engineer and extract all assets, followed by manual review. This works in 90% of the cases.
4. Determine the compression/packing used for the executable. Most binaries used one of roughly five common executable packers.
5. Unpack the executable manually.
6. Use an ancient free IDA-Pro for disassembly, or a modified DOSBox to determine all code/data blocks and the relevant segment-register values for the 8086 architecture.
In the second case I use my vibe-coded disassembler.
7. Identify the major functional domains in the disassembly and split the files accordingly.
...
muro a month ago
you are awesome. I'm doing one such port and it's not that simple :)
ai slop port is not a port, re-creating the full game engine to run in natively a modern cpu architecture that is the challenge
gmerc a month ago
Using a car is not a way to travel, the real way is to take a horse.
hippietrail a month ago
Writing without uppercase letters or full stops is not writing. Low-effort is low-effort. Slop is slop.
mattjoyce a month ago
A few weeks ago I downloaded a memory dump of a zx81 game, and ask Claude to build it in Go.
It nailed it. Converted the binary back to basic and then to go. My idea was that the game would be unknown to llm training and perhaps a nice bench.
What a crazy thing it is to be first at the advent of personal computing, and then in the inflection point where AI treats that first experience as archeology.
rabahs a month ago
Curious if you had to do any follow up prompts. How large was the binary and which model did you use?
EagnaIonat a month ago
I tried this as an experiment with the hobbit tape file to Godot. Worked, and I was quite impressed in how it deconstructed the binary. At one point it did cheat by looking up the zx81 Hobbit online to find pieces that were missing.
btbuildem a month ago
> one copy of the Amiga Hardware Reference Manual
aka The Book... my, this brings back dusty memories
Babylonian Twins has such strong "Gods: Into the Wonderful" vibes, I wonder if that game was an inspiration for you
Ah! How many times I played that game. I missed it on the Amiga after and never unfortunately saw your game. Those old MSX games just had good ideas.
larodi a month ago
"Gods: Into the Wonderful" is perhaps the most amazing and inspiring game of the early 90s that literally blew my mind the first time I played it. Been playing it on and off for more than 15 years afterwards. It is a shame that publisher went down, they also released some other good games, but GODs is the legend among them.
Besides, if it wasn't for BBSs and pirated software, we'd never be ever able to put hands on it, as my country was going through regime change in 1989 and in 1992 the economy was completely mashed down and the game's price was half my mother's salary at the time. What a time to be alive. Of course it was not dad, but a friend who dug it from some BBS or perhaps the eraly tucows archive.
parlortricks a month ago
I remember playing Gods, was a great looking platformer.
dannyobrien a month ago
I just wanted to add how much in awe I am at you creating this game in '93 in assembly. Around the same time I was trying to write a game on the Atari ST, and the dedication to the project -- especially when documentation was so thin on the ground, pre-Internet -- is extraordinary. Do you have any stories from debugging the game? I always found that the most dispiriting part, after the endless hope of handcrafting the code that I was sure would work first time...
rabahs a month ago
Thank you for sharing your experience. It can be hard to remember all the details of debugging in assembly, but the main aspect I recall was managing game performance to ensure all rendering and processing stayed within 1/50 of a second. My technique was drawing a white line using the Amiga Copper, starting at the beginning of the top vertical blanking period. As I added more game objects, logic, and rendering, I had to make sure the line does not drop below the beginning of the active display area. If it went below that point, a frame would be dropped, resulting the game to flicker. I had to use many techniques to split the processing of the game objects in batches across multiple frames. Fun time.
TacticalCoder a month ago
> I spent the last few weeks analyzing what Claude did, feeding it my 33 years of memory of how I built the game, my notes and the git repos. It wrote the first draft of the article, and I edited line by line over a week.
Sooooo cool! I did something similar a few months ago: had the old source code (and executable files) of a game I wrote in 1991 (PC DOS) and a few notes in source code and, well, my old memories of how things worked. I didn't know how to compile it anymore but with the help of LLMs I managed to get it compiling again.
Since then I found about 8 pages of handwritten notes I took back in the days and I did immediately scan them and I added them to the repo.
Now my PC DOS from 1991/1992 does compile again and, well, I really should blog post about it one of these days (if only I had a blog...).
rabahs a month ago
Thanks for sharing. It is truly an amazing feeling when AI helps us excavate the past. I never thought I would be able to do so. I'm so glad I kept all my files over the past 33 years.
rererereferred a month ago
You can pout it on itch.io and write a devlog there.
rabahs a month ago
It is already on itch. Check the babyloninantwins.com for all the links
Gamemaster1379 a month ago
Neat project.I've been experimenting with making reusable console porting frameworks since last October. Opus 4.6 was my first success with the NES 6502.
Since then I've done static/native ecosystems for the Super NES, GBA. Nintendo DS, Playstation (most popular) and even Sega Genesis, such also uses the 68k.
I even extracted the 68k decoder to its own repo because I wanted to reuse it for the Phillips CDI.
Sega does Sonic 1 2 and 3&K. Also Rocket Knight adventures. Still early yet though.
CD-I does the BIOS. Didn't get a game running end to end yet though.
rabahs a month ago
Cool. I wonder how much additional harnesses would improve the porting process. In my case, I gave more freedom to Fable 5. The model was able to figure things out. I am hearing that the latest models works better with less restrictions. Curious to know the progress on the above.
Gamemaster1379 a month ago
If you want to see a bit more in depth, some shameless plugs but here's a few articles I've written as I've made progress:
Ultimately, Sega Genesis has been low priority. I've been focusing mostly on community feedback for my existing ones. Playstation is by far the most popular and the one I get the most PRs on. SNES is second. And right now Nintendo DS is newer, but has a very popular Metroid Prime Hunters I've been working a ton on.
NES and Sega Genesis get little attention. CDI and VirtualBoy [understandably] get no real attention.
I have an early original Xbox LLE prototype. Hoping to do more with it soon, but I'm all tapped out of usage at the moment. I got a lot done during all the crazy resets with OpenAI there for a while.
pixelpoet a month ago
Rocket Knight Adventures!!! Immediately I can hear the music in my head, and I haven't thought about this game in a long, looooong time! Thank you for mentioning it, I'm off to get a Mega Drive emulator :)
cesaref a month ago
I noticed he mentioned that his game was running at 50hz - that's true if an Amiga is running on PAL, but if it's a US machine it'll be 60hz when running with NTSC.
Back in the day, most Amiga games were made in Europe, so were tuned for 50Hz refresh, and played 'normally' over here. At 60hz, they would feel wrong, and likewise, US games could feel sluggish and unsatisfying.
Locking the machine to the monitor refresh rate in this way was a curse but also a blessing. It allowed the machines to drive a standard television in various regions, although the image was somewhat blurry, but also the use of dedicated monitors once you started taking it seriously. This reduced the price point and allowed lots of kids to convince their parents to get one :) The higher resolution modes just didn't work out though, so lots of stuff targeted the 320x256 resolution.
The surprise benefit was also that the amiga could genlock to a TV signal and used to overlay onto a video feed, leading to many interesting cheap graphics overlay capabilities which were otherwise totally unobtainable by small TV channels or enthusiasts.
Those were happy days.
hedgehog a month ago
This is fantastic. It would be interesting to have Claude Code export an engineering guide for doing similar ports, including descriptions of the tooling it built to do it. I've done some reversing from binary but never with results this good.
rabahs a month ago
This is a great idea. It could be a generic game porting skill to make the porting experience smoother. After my experience above. I have actually tried giving Claude binary files of games and it was able to reverse engineer to GoDot!
sedawkgrep a month ago
> I have actually tried giving Claude binary files of games and it was able to reverse engineer to GoDot!
Oh wow...I hadn't even thought of trying something like this. There are soooo many games from that era that I'd love to play again without the hackery of emulation.
ericd a month ago
Yeah, someone reverse engineered Red Alert 2 recently. Took Fable cranking for almost a month, but it's pretty amazing to see.
this is the closest thing I could find. do you have a link to the reverse engineered RA2? I am surprised I do not get any recent repositories or forum posts about this, you'd think it would be more talked about
rabahs a month ago
Just grab any game, especially old rom files form the 80s (I tried TimePilot and Road Fighter from MSX era). The model extracted the graphics, the sounds and then built the whole game. It takes less than 1 hour to port a 16kb rom file, in one shot. You will get a playable game, but you need a few follow up prompts to get it back to its original form. Usually some sprites or sounds issues, but very easy to fix, if you have played the original game.
WarcrimeActual a month ago
So by old ROM files, you mean still PC games or MSX, Sega, NES, SNES? And when you have them in place what do you specifically ask Claude? This is interesting and I'd love to see if it can get me porting old games with zero coding knowledge.
rabahs a month ago
Yes, you can try your game out. I tried with old msx rom files and it worked.
hnlmorg a month ago
Dumb question this, but how do you load it into Claude? I’ve only seen APIs for text and image uploads. Not random files. Or maybe that’s a limitation of the SDK I’m using?
rabahs a month ago
With Claude Code command line, you can point to any directory you have in your file system. In this case, Claude Code was working across three directories: the original game in assembly, the 2010 port in C++, and the new Godot port.
Steve16384 a month ago
This is amazing. How long did that process take? Was it almost just a case of giving Claude the binary files and then prompting "please recreate this in Godot"?
rabahs a month ago
I tried it with 16k roms. It does take less than 1 hour but if you want to tweak and make playable, you will need half day
asimovDev a month ago
session stored on the drive would also contain all of the tool calls , right? unless op changed the default settings it would've expired though by now, since the run was in July
rabahs a month ago
That's a good point. I looked at the git history for my analysis. What is the best way to analyze claude sessions history? I definitely check if I still have them stored. Thanks
asimovDev a month ago
sessions are stored in the home folder somewhere but are deleted after 30 days by default. it won't be stored in the bash history, at least it does not for me on macOS with zsh + omz
b112 a month ago
Of course is one does nightly, off site backups, all is well! A friendly note to all, always have backups!
ecliptik a month ago
I'm doing something similar for DOS SDL ports. Repo isn't public yet, but idea is to have a repo with a knowledge base, skills and patches agents can use when porting to avoid having to bootstrap everything from scratch.
1313ed01 a month ago
Porting to DOS sounds like a great plan for retro games, to only have to do the port once and know there are stable emulators to run it in, as opposed to porting to some modern OS and then have to port the game again and again to keep up with API changes.
ndiddy a month ago
I'm assuming they mean SDL ports of DOS games. SDL is actually one of the most stable libraries that a native game can use. They make breaking changes to the API once every 10-15 years, and they write a compatibility layer that implements the previous version's API using the current version's API as a backend. This has happened twice so far, so there's an SDL 1.2 implementation that uses SDL 2 and an SDL 2 implementation that uses SDL 3. These can be chained together, so for example you can run an SDL 1.2 game from the early 2000s on a modern Linux system and it'll have native Wayland and Pipewire support thanks to using SDL 3 behind the scenes.
robviren a month ago
I'm actually glad to see it stumbled in a few areas. Always surprised to see how much it gets right though. I had always hoped the rather obscure parts of computer history and games would be this incredibly difficult area for Agents to mine.
The amount of non standard hackish and obtuse things that had to be done to implement things in the past feel impossibly complicated to touch today. Lots of people made it up as they went along and used the hardware in ways no one expected. Reminds me of Tim Follin doing the audio for Plock on SNES and Miamoto being shocked the audio was real. It would be so interesting to see what we could learn about development of the past from agentic insights into how code was constructed. I love stuff like this an appreciate the in depth post.
seobotaicom a month ago
Do you think AI could actually help us discover techniques from old games that were never documented by their original developers?
ericd a month ago
Wow, that's gorgeous for something written in assembly, running in 512k, nice work!
efficax a month ago
amigas were way ahead of their time. We had an Amiga 500 and then got a 386 and it was such a downgrade, but the Amiga was clearly a dying system.
ericd a month ago
Yeah, my cousin had one, was like a computer from a parallel evolution chain, kind of weird, but kind of awesome.
nnevatie a month ago
Looks like a pretty de-facto Amiga game of the era, to be honest.
Amiga 500 (and 1000 prior to it) supported smooth scrolling by simply setting the screen-visible pointer in memory.
kschiffer a month ago
I did Moonbase Commander, in JS and HTML canvas. Currently building an AI opponent that doesn't suck as much as in the original.
It's amazing that this is possible. I took quite a bit of steering and was definitely not a one prompt endeavor but having a lot of fun with it.
snvzz a month ago
From the article:
move.l #$dff000,a0 ;Base for hardware registers
lea save(pc),a1 ;Get the system
move.w #$4000,intena(A0) ;from the AMIGA
Crude, although perfectly fine in practice. The system-friendly way is to call the function exec.library has for the purpose, Disable()[0].
Thanks. I wonder if that was documented in the Amiga Hardware Reference Manual :) that was the only book I had back then. I remember it was mostly registers and assembly language.
snvzz a month ago
You're welcome.
It's all in the NDKs, which I didn't have at the time, either. I only got my hands on the AHRM once I started university, and that was after 2000.
Having very belated fun with Amiga development today. It's never been easier to get into, with all the archived tools and books, and the modern ones.
coder-pm a month ago
Hmm did you ever run the game port against the original one in UAE? With the same inputs? Or is it just "it plays right when I play it"? That 108 byte delta is puzzling...
rabahs a month ago
You mean run them side by side ? No, I did not do that. I played the ported game on my Mac only. The movement feels right based on my thousands of hours playing the original. There was only small tweak I had to make the trampoline jump, but everything else ported so smooth. I think the decision that Claude made not to use Godot physics and just port everything as as, made the gameplay feels right without much tweaks.
Lerc a month ago
Have you been following the videos on Youtube of the Amiga port of Sonic?
Their approach to replicating the behaviour is to run the original game logic. The display has to be totally rewritten but they had the advantage of 68k for both machines.
I don't know of any games that used the blitter for calculation like some programs did for MFM decoding, that might have presented quite the porting challenge.
rabahs a month ago
No, I have not. I will definitely check before releasing the Amiga port inside the Steam. I think that would be the right approach, especially if you are porting a game you have not played enough. I did use blitter for all graphics. Now you mentioned MFM, I remember I wrote some disk copy protection code back in the day that leverages MFM encoding. I will check if that code is still around.
coder-pm a month ago
Nice, so it works quite good! So it’s a port, not a re-implementation. Good job on that, I like it that way:) do you have an idea why the trampoline jump didn’t come across?
rabahs a month ago
The trampoline jump physics was correct. The issues was that the 2010 c++ version ignored a held button because of an Apple TV workaround I implemented when I enabled support of tvOS 10 years ago. Godot port read it as pressed, so you get high bounce without a fresh press: https://babyloniantwins.com/blog/porting-a-1993-amiga-game-t...
coder-pm a month ago
Oh so it’s about the platform where it lives, not about the logic, fair enough. Porting logic as is looks like the best approach, the one thing that broke wasn’t really logic:)
Lerc a month ago
There are a few instructions that are functionally equivalent. It is possible that one of the assemblers has the ability to auto convert equivalent behaviour instructions into smaller instructions that do the exactly the same thing. That is fairly common in assemblers. If one of the assemblers had a normalisation phase where they treat multiple forms of the same instruction as the same thing prior to checking if a more compact encoding is possible then that normalisation phase could be generating a same size instruction with same behaviour but with a different encoding. A small number of bytes different with same behaviour is what I would expect from a reassembly like this.
The proof of the pudding would be to have a look at what the differing bytes were encoding.
coder-pm a month ago
Ok but if assembler normalises encoding then a byte diff won’t prove anything. Behaviour check is the way.
Sharlin a month ago
What I'm interested in is performance and memory use. How many times less efficient is the 2010 port compared to the original? What about this new one?
rabahs a month ago
Are you interested in comparing the 2010 remake (C++) to the original (Assembly)? They are quite different games, so hard to compare, but both run at peak frame rate for their respective platforms (60fps vs 50fps).
I have not compared the 2010 port to the current Godot port. However, I felt the Godot port was smoother. I think that was because Godot uses the latest graphics frameworks (e.g Metal) vs old Opengl ES 1. It would also be interesting to compare the godot port of the original game vs the original in assembly. Curious how I can achieve that. A good question to ask Claude.
Sharlin a month ago
> They are quite different games, so hard to compare
Yeah, that's fair. I was just wondering what the performance of a modern version as close to the original would be, if written with Godot or another vastly higher-level framework than handwritten assembly. Given the 3+ orders of magnitude difference in processing power and memory.
rabahs a month ago
The fair comparison is between the assembly version and its godot port. I didn't actually notice any performance difference since th game is capped by its 50 frame per second.
Sharlin a month ago
Yep, at equal resolution the game should presumably run at at least 10000fps uncapped on a modern machine. Of course that's not how it works in practice due to bottlenecks in the input stack and elsewhere.
I also doubt the Godot version fits in 512kB of RAM ;)
abrookewood a month ago
Must be incredibly rewarding seeing your game rebuilt. Fantastic bit of history too - I had no idea games were being made for the Amiga in Baghdad!
rabahs a month ago
The game website link to some articles description the game dev scene back then.
glimshe a month ago
Great work! I'm planning to do that to another forgotten game (not mine) and it's great to see that this is now quite possible.
rabahs a month ago
Thanks! Yes, this was not possible last year, and probably even a few months ago. Amazing times to revive forgotten games and software. Let me know if you have questions on my process.
saulpw a month ago
Which game are you planning to do? We all should coordinate so we're not doing the same games repeatedly.
glimshe a month ago
Ah, it's not going to be Amiga. The shortlist has two PC and two C64 games.
saulpw a month ago
Yeah I'm working on a C64 game myself (Below The Root). Are yours a secret?
glimshe a month ago
Not at all - I'm just not mentioning names because I don't want to discourage anyone to get started before I decide that I'm ready to work on ANY game. If I do it, I'll ping you here :).
byako a month ago
porting a 93 game with an llm reading 68k assembly while i'm over here struggling to refactor last month's javascript. we are not the same. seriously cool project though
ropable a month ago
Thank you to the effort of building this game in the first place (I'm sorry that I never got to try it then), and thank you for re-introducing it to us today. I'll give it a proper play in my leisure time.
rabahs a month ago
Thanks! would love to hear your feedback.
appstorelottery a month ago
Anyone that uses "Claude Fable 5 running in Claude Code"? Can you speculate that plan or cost might have been involved in doing this (given that it seems approximately 5 hours or so of continuous operation for both C++ and Assembly ports, along with the shipping / marketing functions where it's not clear how much compute was used". Thanks in advance (I'm thinking of trying US based models, however I'm penny pinching using DeepSeek Flash etc. ATM).
I have the Max subscription. I use mostly weekends and some evenings. I never hit a limit.
larodi a month ago
Love the GFX and the whole idea that s.o. under sanctions can create this game in 1993 while outside is 50' is itself amazing.
sgt a month ago
Very cool! Wish you had released it back then
rabahs a month ago
Thanks. I know the Amiga version took a long time. It was very hard to even look at the assembly code I wrote after so many years. AI was the hero that explained everything and helped me to package it for releasee. Enjoy!
sgt a month ago
How was Baghdad like in 1993? All I remember from that time was the Gulf war, Saddam and much conflict. I can only imagine how it would be finding hardware, books and resources such a time. That was hard enough even in parts of Europe.
rabahs a month ago
Yes, it was a tough time after the war, but the main difficulty was the economic sanctions, which hit us hard. There are a few interviews and news articles published after I launched the mobile version back in 2010 that discuss our experience in the 90s. You can read more about it here: https://babyloniantwins.com/story/ I am happy to go into more detail on any aspect. I will be watching this thread regularly.
pkilgore a month ago
This was an interesting read, in that it was obvious both that Claude was used in part for the prose but that a human had definitely edited some of the worst claudish out of it (but not enough for me to be able to tell).
Confirmed in that last paragraph. Just interesting to me I can detect gradations of AI speak at this point.
smilbandit a month ago
I've been wanting to do some ports of old games i liked on the atari 400 i had as a kid. some of them I want to see if they would translate to a mobile web game. couple i'm looking to translate are Archon, lode runner, balderdash and maybe some of the ultima games, I really liked ultima 4.
shevy-java a month ago
> The same twin, the same six frames: 1993 above, 2026 below.
But why is the 2026 twin facing right when the original faced left?
It's only a minor detail, but IMO it would be easier for comparison
if they both would point in the same direction.
deterministic a month ago
What an excellent read. This is why I read HN. Thanks!
