David Kalmanson

Entrepreneur, Developer, Investor, Lecturer

[David Kalmanson @davidkal88]

Wow

“Make Red Alert 2 (YR) compile and run natively on iOS & macOS.”

Codex (GPT-5.6 Sol) worked for 26 days, analyzed the EXE and rebuilt the entire game in 624K lines of C++

This is by far the hardest task I’ve ever given Codex as the game's code was never released and is believed to be lost.

>

[David Kalmanson @davidkal88]

@indyjonas You are the king!👑

[David Kalmanson @davidkal88]

https://t.co/AYPDrrrb9m

[David Kalmanson @davidkal88]

What is the next game that I should port? Open for any ideas (but not too large games 😀)

[David Kalmanson @davidkal88]

Wow

“Make Red Alert 2 (YR) compile and run natively on iOS & macOS.”

Codex (GPT-5.6 Sol) worked for 26 days, analyzed the EXE and rebuilt the entire game in 624K lines of C++

This is by far the hardest task I’ve ever given Codex as the game's code was never released and is believed to be lost.

>

[David Kalmanson @davidkal88]

What is the next game that I should port? Open for any ideas (but not too large games 😀)

[David Kalmanson @davidkal88]

@johnny1tap 100% human readable code in this project as the LLM wrote the code

[David Kalmanson @davidkal88]

@winstondu Simply told codex: "The exe is in this directory"

[David Kalmanson @davidkal88]

@n13 I tried Fable. It did an amazing job but was insanely expensive.

[David Kalmanson @davidkal88]

@mattshumer_ check this out

[David Kalmanson @davidkal88]

@Lben /goal mode. but I guided it along the way with inputs . Mainly qa inputs or telling it to stop 'drilling' into something too much (like Internet Gameplay).

[David Kalmanson @davidkal88]

Of course I couldn't have done it without all the resets that @thsottiaux did for everyone. I also used all of my banked resets for this project.

[David Kalmanson @davidkal88]

This post got a ton of attention, so here are answers to some of the questions I got here and in DMs:

1. Had you done anything like this before?

Yes and no.

A few weeks ago I ported C&C: Red Alert and C&C: Tiberian Dawn, but those were much easier because the original source code is available online.

I had never done anything that required Codex to understand and reconstruct a game from an .exe.

2. Why did you do it?

Porting the earlier C&C games felt almost too easy, so I started wondering how much harder I could push Codex.

When I first saw the RA2 game screen running natively on my Mac, I realized this approach could probably work for many other old games too so I wanted to share it partly to inspire others to try.

My personal inspiration came from @ammaar.

3. Did you try other models?

Yes.

GPT-5.6 Luna (x-high) kept spiraling and failed to make meaningful progress.

I also tried Opus and Fable. Both did well, but were insanely expensive at this scale.

4. Is the code human-readable?

Yes. This was one of the most amazing parts.

Codex wrote normal C++ with functions, classes, meaningful names and structure. It doesn’t look like translated assembly or machine-generated low-level code. It looks like something a developer wrote.

It also used online information about the original game(gameplay, rules, etc) so this helped it a lot when creating meaningful variable names and logic.

At one point it even grabbed screenshots from a YouTube video of Yuri’s Revenge and compared them against screenshots of its own implementation to visually check that things matched. (I suggested Codex to do it).

5. Did you guide Codex?

Yes, mostly by pointing out visual bugs.

Its vision still missed quite a few things during visual QA.

The crazy part is that I managed the entire project through the ChatGPT app on my iPhone while on a month-long road trip across the US.

Everything(99%) from my phone.

6. How much did it cost? API or subscription?

About $400.

I used 2 × $200 ChatGPT Pro subscriptions.

I experimented with the API too, but the spending there became insane very quickly for a project of this size.

7. Could you do it faster now?

Definitely.

I think I could probably do it in about a week.

I experimented with running more agents in parallel and it was much faster, but it also burned through credits incredibly quickly, so I had to limit it.

8. What game are you doing next?

I’m not sure yet.

But after seeing this work, I think there are a lot of old games that could potentially be brought back this way.

I’m very open to ideas. What should I try next?

[David Kalmanson @davidkal88]

@ammaar @ammaar Happy you liked it! You are the inspiration👑

[David Kalmanson @davidkal88]

@ryring @ryring really one of the best games ever

[David Kalmanson @davidkal88]

I used Codex to port Command & Conquer: Red Alert to Mac and Android.

No emulation. The original engine now compiles natively to ARM64, with macOS and Android platform layers.

Codex wrote the code, built the binaries, ran them, played the game, found bugs, and fixed them. All in a /goal loop.

(Inspiration from @ammaar )

Full open source below.

[David Kalmanson @davidkal88]

@THOneTwoSix Perfect game!

[David Kalmanson @davidkal88]

@EHuanglu And now this https://t.co/eGtpR68doS

[David Kalmanson @davidkal88]

Wow

“Make Red Alert 2 (YR) compile and run natively on iOS & macOS.”

Codex (GPT-5.6 Sol) worked for 26 days, analyzed the EXE and rebuilt the entire game in 624K lines of C++

This is by far the hardest task I’ve ever given Codex as the game's code was never released and is believed to be lost.

>

[David Kalmanson @davidkal88]

@jskolte @jskolte
Sure, done
https://t.co/eGtpR68doS
😍

[David Kalmanson @davidkal88]

Wow

“Make Red Alert 2 (YR) compile and run natively on iOS & macOS.”

Codex (GPT-5.6 Sol) worked for 26 days, analyzed the EXE and rebuilt the entire game in 624K lines of C++

This is by far the hardest task I’ve ever given Codex as the game's code was never released and is believed to be lost.

>

[David Kalmanson @davidkal88]

@Hamoonist Yep. done
@Hamoonist
https://t.co/eGtpR68doS

[David Kalmanson @davidkal88]

Wow

“Make Red Alert 2 (YR) compile and run natively on iOS & macOS.”

Codex (GPT-5.6 Sol) worked for 26 days, analyzed the EXE and rebuilt the entire game in 624K lines of C++

This is by far the hardest task I’ve ever given Codex as the game's code was never released and is believed to be lost.

>

[David Kalmanson @davidkal88]

@schmoeny @schmoeny it was hard but here you go
https://t.co/eGtpR68doS

[David Kalmanson @davidkal88]

Wow

“Make Red Alert 2 (YR) compile and run natively on iOS & macOS.”

Codex (GPT-5.6 Sol) worked for 26 days, analyzed the EXE and rebuilt the entire game in 624K lines of C++

This is by far the hardest task I’ve ever given Codex as the game's code was never released and is believed to be lost.

>

[David Kalmanson @davidkal88]

@TCGsherpa @TCGsherpa it was hard but it's done https://t.co/eGtpR68doS 😍

[David Kalmanson @davidkal88]

Wow

“Make Red Alert 2 (YR) compile and run natively on iOS & macOS.”

Codex (GPT-5.6 Sol) worked for 26 days, analyzed the EXE and rebuilt the entire game in 624K lines of C++

This is by far the hardest task I’ve ever given Codex as the game's code was never released and is believed to be lost.

>

[David Kalmanson @davidkal88]

@ryring @ryring crazy but it's done. https://t.co/eGtpR68doS

[David Kalmanson @davidkal88]

Wow

“Make Red Alert 2 (YR) compile and run natively on iOS & macOS.”

Codex (GPT-5.6 Sol) worked for 26 days, analyzed the EXE and rebuilt the entire game in 624K lines of C++

This is by far the hardest task I’ve ever given Codex as the game's code was never released and is believed to be lost.

>

[David Kalmanson @davidkal88]

@TannerIngalls @TannerIngalls it was hard but it's done
https://t.co/eGtpR68doS

[David Kalmanson @davidkal88]

Wow

“Make Red Alert 2 (YR) compile and run natively on iOS & macOS.”

Codex (GPT-5.6 Sol) worked for 26 days, analyzed the EXE and rebuilt the entire game in 624K lines of C++

This is by far the hardest task I’ve ever given Codex as the game's code was never released and is believed to be lost.

>