This is a submission for the June Solstice Game Jam

What I Built

SIGNAL is a three-chapter browser game about messages that someone tried to stop, and that got through anyway. Each chapter is its own kind of game, set in a different year, tied together by one idea: the moments that change history usually start with a signal that refuses to die.

Chapter 1: The Machine (1943). You sit at Bletchley Park breaking ciphers on an Enigma-style wheel. The messages you decode were written by people who couldn't say out loud who they were. Crack one, and Alan Turing reads it and talks to you about what you found.

Chapter 2: The Word (June 19, 1865). You become General Order No. 3, the order that reached Texas two and a half years late and finally ended slavery there. It plays as a side-scroller through a greyscale world, and every person you reach restores one stripe of the Pride flag to the screen.

Chapter 3: The Light (June 21, 2026). The game checks today's date. Play it on the solstice and the sky renders differently. Then it looks back at everything you did across the first two chapters, writes you a short personal message, and asks one question: what signal will you send?

That's the theme connection, top to bottom. The solstice is the literal hinge of Chapter 3, since the game knows when June 21 is. Pride runs through the hidden-identity messages of Chapter 1 and the color restoration of Chapter 2. Juneteenth is the entire premise of Chapter 2. June being Turing's birth month is why Chapter 1 exists at all.

Video Demo

Code

GitHub: https://github.com/cybort360/signal

Play it in the browser: https://signal-six-lyart.vercel.app

How I Built It

The stack is small on purpose: Vite, Phaser 4, and the @google/genai SDK for Gemini. No React, no TypeScript. Phaser already hands you scenes, input, audio, and a game loop, so a second framework would just be weight.

A few decisions worth calling out.

Every Gemini call lives behind one file. GeminiService.js is the only place that imports the SDK, and it has two rules it never breaks. It races every call against a 10-second timeout, and it never throws. If the API is slow, errors out, or you're offline, the player gets a hand-written fallback instead of a spinner. I wrote eight fallbacks per call type so the canned lines don't repeat or read as canned. So Chapters 1 and 2 play fine with the network unplugged; only the live Turing lines and the ending reach out.

The cipher is Vigenère, not a real Enigma. Simulating actual rotors would have eaten the whole jam. Vigenère reads as real encryption on screen, it's clean to write as pure functions, and it sits right next to what Bletchley was actually up against. The cipher math has its own unit tests; 55 tests total run on vitest, covering the encoding, the save system, and the AI fallbacks.

Nothing is imported art. The Enigma wheel, the signal particle, the citizens, and the gradient skies are all drawn at runtime with Phaser's graphics API. That kept the build tiny and gave the game one consistent, schematic look without me opening an image editor once.

State carries across the whole game. A single PlayerState object tracks how many ciphers you cracked, how accurately, who you reached in Chapter 2, and what you said to Turing. Chapter 3 feeds all of it into the Gemini prompt, which is why the ending speaks to your specific run instead of a generic one.

The honest messy part: I found a bug late where pressing Enter to skip the Chapter 1 intro leaked into the cipher wheel and confirmed a stray letter, quietly corrupting your first key. It took a real play through to catch. The fix was to drop Enter as a confirm key and keep confirmation on Space only.

It ships to Vercel as a static site. One tradeoff comes with that: the Gemini key gets compiled into the client bundle. Fine for a jam, not something I'd push to production without locking the key to a domain.

Prize Category

I'm submitting for both optional categories.

Best Ode to Alan Turing. Chapter 1 is the whole tribute. It's set at Bletchley in 1943, the mechanic is code-breaking, and Turing shows up as a Gemini-powered character who reacts to what you decode. The deeper idea is the one that haunts his story: he built a machine to uncover hidden messages while having to hide who he was. The messages you decrypt were written by people doing exactly that, and Turing's dialogue keeps circling the gap between the secret you break and the secret you keep.

Best Google AI Usage. I used the Gemini API (gemini-2.5-flash-lite) in two places, and tried to make the AI do something a script couldn't. In Chapter 1, Turing's replies are generated against the actual message you just decoded, so he's answering content rather than playing a tape. In Chapter 3, the model reads your entire play through and writes a personal closing note. I ran it with thinking disabled and a 300-token cap because the writing is short, wrapped every call in the timeout-and-fallback net above, and kept all the prompts in one config file. The result is AI that carries the emotional payoff but can't break the game if the network does.