The instrument
How a voyage works
What the light actually does, how the score follows it, and what the stop is for.
Lie down somewhere dim, and close your eyes
Prop the phone so the light on the back faces you, put headphones on, close your eyes.
For the next five to thirty minutes the torch pulses, the score moves with it, and a voice tells you where you are. Your eyes stay closed the whole way, which is how it works rather than a way of making it gentler: a closed eyelid spreads light across more of the retina, not less.
The light source is the torch, run at a fraction of its full level, in a dim room, at arm's length. Closed eyes are how it works, not a precaution.
There is a stop under your hand the entire time. Touch the lower half of the screen and the light goes out at once, with nothing to confirm. The first voyage makes you use it once, on purpose, so your hand knows where it is before you need it.
It must work for a frightened person with their eyes closed, so it is not a button. It is half the screen.
One curve drives the light and the score together
A world is written as a single intensity curve. The light reads it, and the score reads the same curve at the same clock, so what you hear and what reaches your eyelids are one line, never two things glued together in the mix.
Each world's music is built from loops whose lengths share no common factors, mixed against the same clock the light reads. The combined cycle is longer than the longest voyage, so the fifteen minute version and the thirty are the same music at different rates, and no two runs sit the same way.
Every world without light
Same music, same narration, same lengths, dark screen. This is a full line of the product rather than a consolation prize, and it is what the whole library becomes for anyone the screening closes the light to. It costs the same. A cheaper audio tier was considered and rejected, because it would have priced people by their medical history.
A private atlas
After a voyage you can log what you saw. Entries are named by world and date. The picker's options are not a description of what a voyage produces. The atlas never leaves your phone.
Some people get very little out of this. The light runs the same for everyone.
There is no light on this website
Nothing here flashes, pulses or strobes. The only motion is arrival: as you move down a page, things settle into place once, gently, and are still. Nothing repeats, nothing oscillates, and luminance only ever rises. If your system asks for reduced motion, even the settling is stilled to a plain fade.
One small script does that settling, and nothing else. It makes no request, stores nothing and watches nobody. The security policy this site is served under forbids it from talking to anyone, and the deploy checks read the file itself to hold it to that.
A web page has nobody screened in front of it. Anyone can arrive at one, at any age, in any state, by accident. So the light lives behind the screening, inside the app, or it does not run at all.
The light is not for everyone
Before the torch pulses once, the app asks about seizures, photosensitivity, eye closure, family history, and the symptoms that most often go unrecognised: an unexplained blackout, a lapse in awareness, jerking of the arms or head in the first hour after waking. One episode is enough to answer yes, and Unsure is counted as a yes on every question that closes the light.
A yes to any of the first five closes the light on that phone. There is no button that says you accept the risk, and no version of the light we will sell past that point. What no app can do is stop a person answering the questions a second time with different answers, or deleting it and starting again. The screening works on people who answer it honestly.
The numbers are in the binary, not in the content
The limits below are compiled into the application itself. No world, no update, and no mistake made later can ask your phone for a value outside them. If something tries, the light goes out. The table is stamped onto this page from the same file the build is checked against, and a deploy fails if the two ever differ.
| What | Limit |
|---|---|
| Light frequency | 0.5 to 13.0 Hz |
| Never entered, including during ramps | 13.5 to 25.0 Hz |
| Harmonic energy inside that band | at most 0.35 of alternating energy |
| Modulation depth | at most 0.85 of full |
| Torch level | at most 0.6 of the phone's maximum |
| Duty cycle | 0.15 to 0.50 |
| Unbroken flicker | at most 1200.0 seconds |
| Rest between runs of light | at least 1.5 seconds |
| Flicker across one whole voyage | at most 2400.0 seconds |
The band the light does use is not a band without risk, and the top of it sits inside the wider range published sources treat as capable of provoking a seizure. Where each limit comes from, which of them rest on published sources, which are our own judgement, and what moved on 22 August 2026, is set out in full on the safety page.
What stays on your phone
Nothing that identifies you ever leaves your phone, and nothing you did or felt does either. There is no account and nothing to sign in to. The app sends one anonymous message a day: whole-number counts of how many voyages ran and why they ended, carrying no identifier of any kind, with an off switch in Settings. It downloads new worlds the same way, asking for nothing about you to do it. Purchases are between your phone and Apple. The privacy policy states all of it, line by line.
Your screening answers are not written down at all. The outcome is, and it stays on the phone. So does your atlas. No advertising identifiers, no tracking, nobody watching a session.
Everything a voyage needs is already on the device, so a voyage runs in aeroplane mode, on the free worlds as well as the paid ones.
The app asks for camera permission, and it should say why: on iPhone the torch holds steady timing only while a camera session is open. Nothing is recorded, seen or saved.