Georg PiwonkaThis is a submission for the June Solstice Game Jam What I built Turing's Last Cipher is...
This is a submission for the June Solstice Game Jam
Turing's Last Cipher is a text-based cipher/puzzle adventure. A plain envelope arrives,
postmarked June 21st, full of jumbled letters and one typed line: "For whoever still cares to
listen. — A.T." Your terminal blinks awake, an AI assistant introduces itself, and together
you start decrypting what Alan Turing supposedly never finished saying.
You solve real ciphers — Caesar, Atbash, Vigenère, a dial-it-yourself Enigma — across four
chapters. But the assistant helping you is not as steady as it first seems. Its hints get
slippery. It starts to mislead. And by the end you learn why: these messages were never
written by Turing. They were generated by a modern AI reconstructing him. The closing
question mirrors the Turing Test in reverse — if an AI can reproduce every thought of a person,
is it that person?
▶ Play it now (Cloud Run): https://turings-last-cipher-336966558985.us-central1.run.app
Source (MIT): https://github.com/gpiwonka/turings-last-cipher
🏳️🌈 Overall / Best Ode to Alan Turing. Turing isn't set dressing here — he's in both the
mechanics and the narrative. You break the same families of ciphers he worked with, you
operate an Enigma, and the entire story is an argument about the Turing Test. I tried to handle
his biography — the persecution, the conviction, the loss — with dignity, because that grief is
the emotional core of the ending, not a gimmick.
🤖 Best Google AI Usage. The in-game assistant's hints and dialogue are rendered live by the
Gemini API (gemini-2.5-flash), and the whole thing is deployed on Google Cloud Run.
The interesting part is how the AI is used — see below.
The twist of the game is an unreliable AI, so the engineering question was: how do you let a
language model voice an untrustworthy narrator without letting it break the puzzle?
My rule was a hard separation between truth and wording:
Core library. LLMs corrupt
character-level crypto, so they're simply not allowed near it.So Gemini does exactly what a language model is good at (voice, flavor, character) and nothing
it's bad at (being the source of truth).
/api/*. Blazor WASM (not Server)
was deliberate — it avoids a persistent SignalR circuit, which is fragile on Cloud Run's
scale-to-zero.content/scenes/story.json) with a startup validator that
catches dangling links and unsolvable puzzles before shipping.Dockerfile; the server honors the
injected PORT.The thing I'm proudest of is that the unreliable-narrator twist is also the architecture: the
game is, at every level, about an AI that can sound exactly like a trustworthy source while not
being one — and the code is built so that the model is allowed to sound like anything while
the truth stays provably elsewhere. That separation is the whole point of the Turing Test, and
it turned out to be the whole point of the build too.
Thanks for reading — and for playing. Decrypt carefully.