This is a submission for the June Solstice Game Jam
What I Built
The Longest Night is a browser game about codes, daylight, and one impossible question.
It's June 21 — the solstice — and you're the night-shift cryptanalyst at a remote listening station. Four encrypted transmissions arrived at noon. Command wants them broken before the sun goes down, and the sun is going down: an animated sky drains from afternoon gold to starlight in real time as you work. Wrong answers and hints burn extra daylight. If night falls, you finish by starlight — and the ending remembers.
The four transmissions walk you up a small history of cryptography: a Caesar shift you crack by feel with a dial, a turned-around alphabet you read through one of three lenses, a Vigenère cipher whose keyword is hidden in the story itself, and finally a rotor cipher that advances with every letter — a quiet nod to Enigma. The answers are drawn fresh every watch, so no two runs solve alike.
But the game's real subject sits between the levels. Your only company all night is C, a colleague at the other end of the teletype line. C is curious, wry, a little melancholy. C asks whether you felt the keyword or computed it. And when the last transmission is broken, C asks you the only question that matters:
"You have talked with me all night, watched me think, or seem to. One question, and answer honestly: what am I?"
Human? Machine? It doesn't matter? You choose — and the game tells you the truth.
Why this fits the theme: the solstice isn't set dressing — daylight is literally the resource you spend, and the passage from the year's longest light into its first night is the game's clock, its soundtrack, and its title. And June is Alan Turing's birth month: the whole game is an inversion of his 1950 imitation game, where this time you sit in the interrogator's chair. Even C's name comes from Turing's paper — player C is the interrogator who must tell human from machine.
🎮 Play it here (free, browser, ~10 minutes): https://newdawnera.github.io/solsticegame/
Video Demo
Code
newdawnera
/
solsticegame
A solstice codebreaking game — race the setting sun through four ciphers, then answer Turing's question: was your only companion human, or machine? Built for the DEV June Solstice Game Jam 2026.
The Longest Night
A solstice codebreaking game for the June Solstice Game Jam.
You are the night-shift cryptanalyst at a remote listening station on June 21. Four encrypted transmissions must be broken before the sun goes down. Between ciphers, you talk to C — a colleague on the teletype line — and at dawn you must answer Turing's question: was C human, or machine?
Play it: newdawnera.github.io/solsticegame — or open index.html in any modern browser. No build, no dependencies, one file.
The mechanics
- Daylight is your resource. It drains in real time (~8 minutes of sun). Wrong transmissions cost 20s, hints cost 45s. If the sun sets, you finish by starlight — the ending remembers.
- Four ciphers, rising difficulty: Caesar shift → lens cipher (mirror, half-turn, or backwards) → Vigenère (find the keyword from narrative clues) → rotor cipher (progressive shift, an Enigma nod). The dial shift, lens, and…
How I Built It
One file, no engine. The game is a single self-contained index.html — vanilla JS, Canvas for the sky simulation (sun arc, color-graded day/dusk/night gradients, twinkling stars), CSS for the teletype-era UI. No build step, no dependencies.
The ciphers are real. Caesar, Atbash/ROT13/reversal lenses, Vigenère, and a progressive-shift rotor cipher are all implemented and encoded at load from plaintext — the decoder tools you're given (dial, lenses, keyword field) apply the genuine inverse transforms. The dial shift, rotor start, and lens are randomized each playthrough, and the hints adapt: every possible answer has its own in-character riddle. A small dictionary makes English words glow gold in the preview as you get close, which turned out to be the single best UX decision in the project: it teaches the game without a tutorial screen.
Daylight is the only resource. The whole game runs on a single counter: daylight starts at eight real minutes and drains a second per second, mapped to an in-game clock that ticks from 16:04 toward 21:58. Spending it is deliberate — a wrong transmission costs 20 seconds, each hint costs 45 — but the design choice I'm proudest of is that the cost only lands when you commit. Turning the dial, swapping lenses, or typing a keyword is free; it just updates the live gold-glow preview. So the game rewards probing and only ever charges you for guessing. Let the counter reach zero and night falls — you finish the last codes by starlight, and the epilogue records whether you beat the sun (it grades the run Perfect Day, Before Sundown, or By Starlight). The solstice isn't a backdrop here; daylight is literally the thing you're spending.
The soundtrack is code, too. No audio files — the score is generated with the WebAudio API: a music-box arpeggio over a four-chord progression, one of three procedural tracks chosen at random each visit. A low-pass filter is tied to the daylight value, so the music literally darkens as the sun sets. All the interactive sounds (teletype clatter, dial ticks, chimes) are synthesized oscillator envelopes.
C is a three-tier system. This was the most interesting engineering problem: how do you put a live AI in a free, static, client-side game safely?
- Tier 1 — a gated Cloudflare Worker proxy. The Gemini API key lives server-side as a secret. The Worker only accepts requests from this game's origin, rate-limits per IP, caps input and output sizes, and enforces C's persona server-side — so the endpoint is deliberately useless as a general-purpose proxy. All it can do is talk like C.
- Tier 2 — bring your own key. Players can paste a free Google AI Studio key that never leaves their browser.
- Tier 3 — a scripted C with keyword-aware responses, so the game is fully playable offline with zero AI.
The game degrades through these tiers silently — if the shared free-tier quota ever runs out, C just gets a little more predictable.
The ending is honest. Whatever you answer at dawn, the game discloses which C you actually talked to — Gemini or the script. The hesitation before you answer is the point. That was Turing's point, too.
My workflow. I built this by hand as a single index.html — no engine, no framework, no build step — and tuned it live in the browser: how fast the sky drains, the resistance of the dial, the exact moment a decoded word starts to glow gold. The hardest part wasn't the ciphers but making C safe to ship to strangers, so I kept iterating on the Cloudflare Worker until the Gemini key was fully server-side and the line degraded gracefully from live AI, to your own key, to a script.
Prize Category
Best Ode to Alan Turing. The game is built around Turing top to bottom: codebreaking as the core mechanic, ending on a rotor machine; an imitation game where the player takes the interrogator's seat (C is named for the interrogator in Turing's 1950 paper); the third transmission decodes to a paraphrase of his famous reframing — "Can machines think?" is the wrong question; and the epilogue at dawn honors the man himself — born in June 1912, the codes he broke, the question he asked, and the persecution he suffered for being gay. The longest light, for someone made to work in the dark.
Best Google AI Usage. C is powered by the Gemini API (Flash models, free tier) — not as a gimmick, but as the game's thesis: it's a Turing Test run on an actual AI. The integration is production-shaped: a Cloudflare Worker keeps the key out of the client entirely, locked to the game's origin, rate-limited per IP, with the persona and token caps enforced server-side and replies trimmed to complete sentences. Model selection falls through a list of current Flash models automatically, and the whole system degrades gracefully to a player-supplied key, then to a script. Judges get live AI with zero setup — just open the game and talk to C.
Thanks for reading — and if you play just one minute of it, make it the last one. Answer honestly.