What is Codex ET-2?
Codex ET-2 is an iOS app that holds every 8×8 monochrome icon that can exist. Each icon is sixty-four pixels, on or off. That gives a catalog of 264 icons. Eighteen quintillion of them. The app drops you somewhere in that catalog and lets you walk.
The catalog has no curation, no editors, no popular section. Every icon has a permanent home address. The same address resolves to the same icon on every phone. The library is the mathematics.
Codex ET-2 is part of our ET series: pieces built to think about something out loud. In this case, the gap between what a combinatorial space contains and what a human can ever see of it.
Install
Codex ET-2 is in beta on iOS. Once you have access via TestFlight, install it from the link in your invite mail. The app needs iOS 18 or later. On iOS 26 it picks up Liquid Glass styling for the navigation buttons.
There are no accounts. There is no sign-in. The app keeps your saved icons locally on the device.
Your First Walk
Launch the app. A single icon fills most of the screen, with hints of its neighbors poking in from the edges. Below it: an X and a Y coordinate. That pair is the icon’s address in the warehouse.
Try this in order:
- Swipe the icon area in any direction. The camera glides one cell, and a new icon takes the focus. Swipe again. You are walking the warehouse on foot.
- Use the directional pad at the bottom right. Up, down, left, right — same effect as swiping, but a precise one-cell step you can chain quickly.
- Tap any pixel inside the focused icon. The pixel flips on or off. You have just teleported to a one-bit neighbor of the icon you were on — almost always a cell nearby in the catalog, sometimes literally next door. (See Inside the Warehouse for why.)
The Teleports
Walking one cell at a time is fine for browsing a neighborhood. The catalog is too large for that to be your only option.
The two buttons on the bottom left are long-distance teleports:
- WANDER drops you somewhere new. Almost always noise, occasionally something that looks like a face.
- SIGIL folds the draw into a symmetry, and symmetry reads as intent — the icon looks deliberate even when it isn’t: a glyph, an emblem, sometimes a narrow figure standing upright.
Each teleport lifts the camera off the warehouse floor, cruises to the new address, and descends onto it. You see — and hear — the whole journey.
There is a third way to cover ground when you know where you are going: tap the X or Y coordinate under the icon, type an address, and the camera flies straight to that cell.
Saving What You Find
The toolbar at the very bottom of the screen has the live-with controls:
- Back returns you to the previous icon.
- Favorite stores the current icon in your local library.
- Favorites list opens the grid of everything you have saved.
- Share sends a render of the current icon to anyone you like. Its coordinate is encoded in the image filename, so the receiver can teleport back to the exact same address.
You will not find half of these icons twice on your own. Save the ones that mean something.
Where to Go Next
- Features. A detailed map of every control, gesture, and behavior in the app.
- Inside the Warehouse. How the catalog is laid out. Hilbert curves, Gray code, and why one-bit neighbors land next to each other.
- The Library of Babel. The Borges story Codex ET-2 takes its frame from, and what changes when the library is finite.
- Back to the product page.