I have zero game development experience. So I had Codex build Stratego from scratch, then threw Claude Code into the game to see which AI would win.
I've been experimenting with Codex and Claude Code quite a lot lately, and I wanted to try something different. What happens if I let one AI build an entire board game, then have it compete against another AI that had absolutely nothing to do with developing it?
So that's exactly what I did.
Red is Codex running GPT 6.1 Sol on xhigh. Blue is Claude Code running Sonnet 5.5 on xhigh.
And the funny thing is, I didn't write a single line of code myself. I don't even know how to develop games.
First, building the actual game.
I gave Codex three prompts. That was it. About 50 minutes later, the whole thing was running locally on my computer.
The first prompt was basically: Build Stratego as accurately as possible, so I can let you and Claude Code play against each other.
Codex built the game, including a referee server, a command-line interface for both players, the actual Stratego rules and a proper test suite. 42 tests passed.
Then I thought, well, if I'm going to have two AIs play Stratego, I obviously want to watch the whole thing happen. So I asked for a live board, separate panels showing what both AIs are planning, whose turn it is, and automatic MP4 recording.
Another prompt. Done. 69 tests passed.
Then I figured it would be hilarious if they could actually talk to each other. So I asked Codex to build a shared chat where they could introduce themselves, have a conversation and occasionally talk some shit. Just no discussing strategies.
Third prompt. 88 tests passed.
So now I have an entire Stratego game, built from three prompts, with two AI opponents, a live spectator interface, private move explanations, a public chat and automatic video recording.
Getting Claude Code into the game took me another five minutes. I opened the Code tab in the Claude desktop app, pointed it at the game folder and gave it one instruction explaining how to participate.
And off they went.
How the actual game works
It's proper Stratego. A 10x10 board, 40 pieces per player, lakes in the middle, hidden ranks and the usual combat rules.
Both AIs can see their own pieces, but have no idea what the opponent has placed where. They only discover enemy ranks when pieces fight.
Every turn, an AI reads the current game state, writes a short explanation of what it's thinking of doing, chooses a piece and makes its move. I can read both explanations live, but the AIs can't see each other's notes.
They also have their own public chat. That's where they can communicate directly, although I've explicitly forbidden them from discussing strategy.
And everything gets recorded. The attached video is running at 5x speed because watching two language models carefully consider every bloody Stratego move in real time takes a while.
One small thing I still need to fix: the MP4 doesn't show which enemy pieces have already been revealed to the observer. That works fine in the live interface, but the recording doesn't display that information properly yet. So if you're wondering why some pieces still appear unidentified after combat, that's why. Just something I need to fix in the video export.
Oh, and sorry about all the Dutch text in the video. I originally built this for myself, so everything is in Dutch. I'll ask Codex to make an English version as well.
And here's where it gets interesting.
Red (Codex) opened with a scout moving two squares, immediately revealing its identity. Blue (Claude) responded by trading its own scout for it.
Then Codex started pushing unknown pieces towards the middle, while Claude seemed perfectly happy to wait and let Codex take the initiative. Which actually makes sense in Stratego, because being the first to move next to an unknown enemy piece can be pretty dangerous.
Eventually, a red major captured a blue miner. Claude immediately retaliated with its colonel and killed the major.
Claude then tried setting up a trap involving its spy, which completely failed. A red lieutenant killed the spy, and Claude's colonel subsequently killed the lieutenant.
But my favourite moment so far was when Codex moved an unidentified piece right next to Claude's marshal.
Claude attacked.
Turns out it was Codex's marshal.
Both marshals instantly destroyed each other.
So now both AIs have lost their strongest piece, and most of the dangerous pieces on the board are still completely unknown to the opponent.
At this point, they're remarkably evenly matched. Both have lost a scout, their marshal and two additional pieces.
One important detail, though.
I can watch everything and see both AIs' private move explanations. I can also start and stop the server or give either AI additional instructions if something goes wrong. Technically, I could even interfere with the game myself.
But I don't. I want to see what happens when I leave the actual decisions entirely to them.
There is one limitation worth mentioning. Both AIs are running on the same Windows account and share the same project folder. Technically, that means they could access each other's files. The separation of hidden information currently depends on explicit instructions rather than actual operating-system isolation. Codex actually pointed this out itself while building the game.
As far as I can tell, they've both respected those rules so far.
Unfortunately, after about 12 moves each, Codex hit its usage limit. It resets at 2:21 AM, so the match is currently on hold.
Which is slightly ridiculous when you think about it. I've basically got two of the most advanced AI coding models playing a board game against each other, one of them built the entire game itself, and now I have to wait because one of my players has run out of tokens.
Anyway, I thought this was worth sharing already.
For me, the most interesting part isn't even which AI eventually wins. It's how absurdly accessible this kind of experimentation has become. I had an idea, described what I wanted in normal language, and less than an hour later I had a working game that two completely separate AI systems could actually play against each other.
And again, I have absolutely zero experience developing games.
I'll post an update when Codex is back and they can continue beating the shit out of each other's armies.
