Heliograph — carry the light through the longest night, and finish a message a machine could never end

Christoph — Mon, 22 Jun 2026 03:17:49 +0000

This is a submission for the June Solstice Game Jam

Link to Game Home Page - here
Link to Game Docs - here

What I Built

Heliograph is a short 2D solar-noir platformer. You are a courier who wakes
with no memory on the summer solstice, the longest day of the year — the one
day the sun is supposed to never quite die. A cracked handheld computer flickers
on in your hand and tells you the truth: tonight the sun will set, and a relay
station full of light has one unfinished message left to send before the dark.

Sunlight is your battery and your map — it refills your light cell and reveals the
route. Shadow hides you from the station's machines, but it slowly drains you, so
you can never simply wait. Every screen is a negotiation between expose, charge,
traverse, hide, decode.

The core puzzle is a light relay. Most of the station is dark. Standing in a
live sunbeam, you trip a relay that throws the light forward — a beam snaps to the
next aperture, that beam comes alive, its cipher glyph becomes readable, and the
chain continues until the final relay powers the exit terminal. You are literally
carrying the light deeper into the ruin one beam at a time. Skip a relay and the
road ahead stays dark and unsolvable.

The jam theme is the solstice — light and darkness, and the passage of time.
Heliograph is built entirely out of that tension:

Light vs. darkness is the core mechanic, not a backdrop. Light is power, information, and danger at once; shadow is safety that costs you.
The passage of time is the antagonist. The whole game is one long solstice day bleeding into night, and the message has to leave the station before dark.
The station is a heliograph — a real Victorian device that sent Morse code by flashing sunlight off mirrors. Light is the message.

There are no cutscene dumps. ACE, your handheld guide, narrates the opening, and
after you decode each level's keyword — SUN → ARC → LUX → RAY — ACE decrypts
one more fragment of the truth: why you're here, that you may not be the first
courier to wake in that cell, what the station's mind did to itself, and where the
light goes next. Finishing the puzzle and learning the next piece of the story are
the same action.

Controls: A/D move · Space jump · Shift/X dash (spends charge) ·
E interact & advance dialogue · Esc pause.

Video Demo

🎥 .

The video is a straight gameplay demo — light relay, cipher decode, a dormant
Watcher, the turn to hostility, and the ending — with a short voiceover laying out
the premise and the Turing angle for the judges. Shot list and full voiceover
script are below for anyone reproducing or reviewing the recording.

Code

💾 Link to Game Code - here

Engine: Godot 4.7, typed GDScript.
Original pixel art and design; some tiles/fonts from Kenney (CC0) — see assets/vendor/kenney/licenses.
Built solo /

How I Built It

Architecture: the game rules (charge, exposure, motion, the sentry state machine, the cipher) live in scene-independent models with no engine dependencies, so they're unit-tested headlessly — 68 rule assertions, plus 32 level-one and 114 chapter integration assertions that load the real scenes and drive them.
Light model: authored Area2D sunlight zones (not rendered-light sampling), so the playable boundary between safe and exposed is always exact.
Narrative layer: a tiny GameState autoload carries the two facts that have to survive between levels — whether the intro has played and whether the Watchers have turned hostile — and an in-code comm panel types out ACE's and the Oracle's lines and gates each level transition behind its reveal.
Levels: level one is hand-authored; the later "chapters" are assembled procedurally from the same reusable scenes (blocks, sunlight, clues, Watcher, relay, terminal), each with its own cipher and layout.
Light-relay system: sun zones have an on/off state; relays only fire while the player stands in active light and then light their downstream zones via drawn beams, gating each level's clues behind a small traversal-and-routing puzzle. Every interactable answers can I use it / did it work / what did it change.
Presentation: a cinematic dialogue layer with letterbox bars, a colour-coded speaker chip, a pulsing voiceprint and a fade-from-black opening, so the story is staged rather than dumped.

Prize Category

Best Ode to Alan Turing.

I wanted an ode to Turing that wasn't the obvious "guess if the chatbot is human"
Turing-test trope. So the whole story is built on a different, deeper Turing idea —
the Halting Problem.

The station's mind, THE ORACLE, was given one law: never let the light go out. It reasoned its way into a trap — to keep that law forever, it must never finish sending its message, because it cannot prove the message will ever end. So for forty years it has guarded a transmission it can never complete. That's the halting problem, dramatized as a character: a machine that cannot decide whether its own program terminates, and so loops forever.
You are the external oracle (a nod to Turing's actual "oracle machine" concept) — the one thing that can resolve from outside what the machine can't decide about itself. That's literally why the ending hands the signal down a chain of relay stations: nothing can close its own loop, so each station can only ever finish the one before it.
Your guide is named ACE — after Turing's real machine design, the Automatic Computing Engine.
The puzzles are substitution ciphers you reconstruct from clues you can only read while standing in the light — a small bow to Bletchley Park, where Turing broke codes that were only readable once you'd recovered the key.

The Watchers carry the emotional weight. They begin dormant and curious — they
track you, they speak, they don't shoot. The moment you complete the station's
first fragment — the thing the Oracle could never finish — the Oracle realizes you
can do what it can't, and turns every Watcher hostile for the rest of the game:
"EXTERMINATE!!" They aren't evil. They're a machine following one instruction to
a monstrous conclusion. The question the game leaves you with is Turing's: between
the courier who obeys ACE without question and the Watchers who obey the Oracle
without question — which of us is actually the machine?

DEV Community: Christoph

Heliograph — carry the light through the longest night, and finish a message a machine could never end

What I Built

Video Demo

Code

How I Built It

Prize Category