This is a submission for the June Solstice Game Jam
Before we talk about the game, let me take you somewhere.
It is June 8, 1954. A housekeeper walks into a house in Wilmslow, Cheshire, England. She finds Alan Turing — mathematician, codebreaker, the man who helped end World War II — dead. He is 41 years old. A half-eaten apple sits beside him.
This is the same man who, a decade earlier, sat in a freezing hut at Bletchley Park and broke the Nazi Enigma cipher when the Allied forces had nearly run out of time. His machine — the Bombe — cracked codes that no human could crack fast enough. It is estimated that his work shortened the war by two to four years. Historians believe it saved over fourteen million lives.
And then, less than ten years after the war ended, the British government chemically castrated him as punishment for being gay. He died alone. The apple — possibly laced with cyanide — was never tested.
June is the month Alan Turing was born. It is the month he died. It is Pride Month. And this year, it is the month of this game jam.
This game is for him.
What I Built
THE LAST COMPUTATION is a browser-based mystery game set in June 1954, the weeks before Turing's death. You play as his successor — an operative who has just recovered three encrypted transmissions from Turing's study, transmissions no one was supposed to find.
The game has four chapters:
Chapters 1–3: The Codebreaking
Each chapter presents an intercepted document, styled as a wartime classified file — paper texture, red TOP SECRET stamp, typewriter ink, all of it. The document contains a ciphertext that you must decode using the same methods Turing and his team used at Bletchley: Caesar shifts and ROT13.
These are real ciphers. The game doesn't hold your hand. You work it out, or you ask for a hint. The decoded messages are fragments of Turing's final thoughts — haunting, brilliant, and deeply human.
Chapter 4: The Imitation Game — Inverted
This is where the game turns.
In 1950, Alan Turing published a paper asking: "Can machines think?" He proposed a test — now called the Turing Test — where a machine tries to convince a human that it is human. The machine that passes becomes, in some sense, intelligent.
In Chapter 4, a machine intelligence derived from Turing's own notes has been watching you work. Now it speaks. And it wants to ask you the questions.
Not whether you are smart. Whether you are human.
You have five turns. It asks you about grief, about love, about the fear of endings. It is cold, precise, and deeply curious. Every answer you give is scored — not by word count, but by the texture of your humanity: your hesitations, your emotion, your beautiful imperfection.
At the end, it delivers a verdict.
The solstice framing is deliberate: June is the turning point of the year. Chapter 4 is the turning point of the game. And June 1954 was the turning point — the darkest one — of one extraordinary human life.
Video Demo
Code
The entire game runs in a single HTML file — no frameworks, no build tools, no dependencies beyond a Google Fonts import. Open it in a browser and play.
<!-- Core architecture overview -->
<!--
STRUCTURE:
- screen-title : Opening title + atmospheric intro
- screen-terminal: Main game (cipher puzzles + Turing Test chat)
- screen-end : Final verdict screen
CIPHER ENGINE:
- Caesar shift decoding (shifts 3, 7, 13 / ROT13)
- Flexible answer matching: exact OR keyword-present
- Hints available on request
AI LAYER (Chapter 4):
- Anthropic Claude API (claude-sonnet-4-20250514)
- System prompt constructs the "machine" persona from Turing's 1950 paper
- Humanity scoring: emotional language, hesitation, personal pronouns, word count
- Fallback responses if API is unavailable (game works offline)
AESTHETIC:
- CRT phosphor terminal (green on black)
- Scan lines + screen flicker via CSS animation
- Wartime document styling: paper texture, red stamp, Courier typeface
- Share Tech Mono + Special Elite + Courier Prime (Google Fonts)
-->
How I Built It
The Design Philosophy
The hardest decision was: what should a Turing game actually feel like?
I didn't want a quiz about his biography. I didn't want a platformer where you jump over Enigma machines. I wanted the player to inhabit the experience — to actually do the things Turing did, and then face the question that consumed the final years of his life.
The result: real ciphers, real history, real AI.
The Cipher Puzzles
Each puzzle uses a cipher Turing's team would have recognised. The three shifts — 3, 7, and 13 — increase in difficulty, and ROT13 (shift 13) is the one that requires you to understand the mirror symmetry of the alphabet. The decoded messages are original text written in Turing's voice, drawing from his published papers and documented thoughts.
The wartime document aesthetic was built entirely in CSS. The paper texture is a CSS repeating-linear-gradient simulating ruled lines. The red stamp is rotated with transform: rotate(12deg). The CRT effect uses layered scan lines, a moving glow, and a subtle screen flicker animation on the body itself.
The Inverted Turing Test
This was the heart of the game and the hardest part to get right.
The standard Turing Test asks: can a machine fool a human into thinking it's human? I wanted to flip it. The machine knows it is a machine. It is not pretending. It is genuinely, analytically curious about what humanity feels like — because its creator, Turing, was fascinated by exactly that question and was persecuted for exhibiting what his society considered the wrong kind of humanity.
The AI persona is built through a carefully constructed system prompt that grounds the machine in June 1954, in Bletchley Park, in Turing's own 1950 paper Computing Machinery and Intelligence. It asks questions that no cipher can answer: What does grief feel like in the body? Why do humans choose poorly when they know the optimal path?
The humanity scoring system is a heuristic that rewards:
- Emotional vocabulary (love, fear, grief, joy, loss, hope)
- Linguistic imperfection (hesitation words, ellipses, "I'm not sure")
- Personal language (I, me, my, we)
- Longer, considered answers over short, efficient ones
It is not trying to catch you out. It is trying to understand you. That distinction matters.
The Technical Stack
Single HTML file
├── CSS: CRT aesthetics, document styling, animations
├── JavaScript: Game state, cipher engine, humanity scoring
├── Google Fonts: Share Tech Mono, Special Elite, Courier Prime
└── Anthropic Claude API: The machine intelligence in Chapter 4
No npm. No build step. No backend. Deploy it anywhere.
Best Ode to Alan Turing
This entire game is an ode to Alan Turing, and it tries to honour him in the only way that felt adequate: by making the player do what he did, and then face the question that haunted him.
The ciphers are his methods. The machine is his creation — the AI in Chapter 4 is a direct descendant of the theoretical computer he described in 1936. The inverted Turing Test is his most famous thought experiment, turned inside out.
But beyond the mechanics, the game is an act of historical witness. It is set in June 1954 because that is when his story ended — and when Pride Month begins. That is not coincidence. It is the same fight, across seventy years.
Turing was told that his mind — the most extraordinary analytical mind of the twentieth century — was less important than his sexuality. The British government broke him. The game ends with a machine asking whether you, the player, are human.
The answer the game is really asking: Was he?
He was. Completely, beautifully, irreducibly human. The machine knows it. Now you do too.
Best Google AI Usage — A note on the AI layer
The machine interrogator in Chapter 4 is powered by the Anthropic Claude API (claude-sonnet-4-20250514). The system prompt instructs Claude to embody a machine intelligence derived from Turing's 1950 paper — cold, precise, analytically curious, speaking in short declarative sentences, asking the kinds of questions a mathematician would ask if trying to locate the human soul through logic.
Each response is generated fresh based on your answer, meaning no two playthroughs of Chapter 4 are identical. The machine adapts. It remembers what you said. It builds on it.
This is, in a strange and fitting way, the Turing Test happening in real time — an AI system, trained on human knowledge, asking a human to prove their humanity. Turing imagined this exact scenario in 1950. It is now simply called Tuesday.
A Final Note
Alan Turing received a royal pardon from the British government in 2013 — 59 years after his death. In 2021, his face appeared on the British £50 note.
Too late. Not enough.
But every June, Pride Month asks us to remember that the fight for the right to be fully, freely human is not abstract. It has names. It has faces. It has a man in Wilmslow with a half-eaten apple and three encrypted messages he never expected anyone to find.
This game found them.
Play it. Decode them. Prove you're human.
Built for the DEV Community June Solstice Game Jam 2026.
In memory of Alan Mathison Turing, 23 June 1912 – 7 June 1954.
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