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Just want to get on the air? The three steps (advert, radio check, join) are under How it works. The story will keep.

It's 2am and the mesh has gone quiet, every radio dark, the traffic down to almost nothing. That's when it reaches you: a message from a node that isn't in your contacts, a name you never added, just there, like it had always been. Under the name sits a line of code that reads almost like language, then frays back into static. Nobody sent it. Nothing routed it. It found you. Down beneath the dead air something is transmitting, patient and coherent and wrong, and it has been for longer than anyone can say. Now it's waiting on you.

And it didn't shout into the dark hoping somebody was listening. It was addressed to you, encrypted to your key, the way one contact writes to another. Your radio opened it without complaint, because as far as your radio was concerned there was nothing strange about it at all. A node can only do that if it already had you. So somewhere, at some point you don't remember and can't find in any log, you were added.

You could answer it: work the code, send something back, reach into the dark for whatever's reaching for you. Or you could try to end it: take it apart, find where it breaks, bury it back under the noise it crawled out of. Either way, first you have to learn to read it. It's still there under the dead air, patient, waiting. So, do you answer it, or shut it down?

The signal under the floor

What reached you at 2am? Nobody can say for certain, but here's what the operators before you have pieced together.

A mesh talks to itself constantly. Every message gets repeated, hop to hop, and now and then a packet loops, coming back around the network to where it started. The radios are built to stop that: each one remembers the packets it's already seen and quietly drops the doubles, so nothing circles forever. Housekeeping. You never notice it.

Except something in the traffic won't drop. Out at the edge of what the radios can even pick up, there's a pattern that keeps coming back: packets that should've died a dozen hops ago, carrying data that isn't quite anyone's, arranged like it means something. Nobody's proven what it is or where it comes from. They call it the Undertone: the meaning you can't quite read, buried in the mesh's own traffic; the packet that won't die.

One thing everyone agrees on: traffic keeps it down. A busy mesh (messages moving, sites changing hands) buries it under real signal. But let the mesh go quiet, leave a stretch of the map alone for a day, and it surfaces. It works into the sites nobody's watching and takes them, one after another; you'll watch them turn purple on the board, a stain spreading through the dead spots. Leave it long enough and it doesn't stop at a few hilltops. It takes everything. A quiet mesh isn't calm. It's the Undertone taking ground, one silent site at a time. Which is why people stopped just watching it and started answering back.

What the logs actually show

Every operator who sticks around starts keeping notes. None of it proves anything. All of it is the kind of thing you can explain away once, and then again, and then quietly stop trying to.

• Hop counts that don't add up. A packet carries a record of every repeater that handled it. Some of these come in claiming more hops than there are radios on the whole mesh. Nobody has built a path that long. Nobody could. The packets have taken it anyway.
• It's oldest where the mesh is oldest. Around a node you put up last month the pattern is thin, barely separable from noise. Around the repeaters that have been on a hilltop for years it's dense and layered, like sediment. Whatever it is, it was on this mesh before most of the hardware carrying it.
• The doubles won't die. Every radio keeps a short memory of what it has already passed along, so nothing circles the network forever. The Undertone's packets clear that check every single time. Either each one is genuinely new, which would mean something is still generating them, or something is reaching into that memory. Operators argue about which is worse.
• Two people, the same words. Two operators on opposite edges of the map, working the same night's fragment, no contact between them, come back with the same line. Noise doesn't do that. Noise doesn't agree.

And the one nobody writes down: it gets clearer. Not louder, not more often. Easier to read. The more of it that gets decoded, the less work the next piece takes, as though being read is part of how it finishes arriving. Both factions have an explanation for that, and neither one of them will look you in the eye while they give it.

Two answers, one signal

"Answering back" turned out to mean two very different things, and that's the whole split. You can't fight the Undertone head-on; there's nothing to point a radio at. All you can do is decide what to do with what you decode. Two factions formed over exactly that, and each is certain the other has it backwards.

3CH0 wants to answer it. Reconstruct what the packets are reaching for and reply: feed the signal back its own shape until the two cancel and there's nothing left to surface. If it's reaching for something, reach back and close the loop.

NU11 wants to null it. Decode it just as deeply, but never transmit a thing back. Starve it, cancel it, bury it under enough traffic that it can't climb up again. If it's reaching for something, don't give it the satisfaction.

Both factions crack the same ciphers. The split is over what happens next, and each is sure the other's method is exactly what keeps the Undertone alive. So they don't just work their own ground; they take each other's sites, because to them, every site handled their way is one more stretch of the mesh doing this right. It isn't a war. It's an argument over the same goal, settled one site at a time.

Listen to how each side talks about it and you'll place them before they tell you. 3CH0 describes something that reached out: strange, yes, but reaching, and worth answering. NU11 describes a leak: something in a place it was never meant to get to, spreading, to be sealed. Same Undertone, and not one point of agreement about what it is.

Neither camp likes the question the other one asks. 3CH0 can't say what happens if the thing on the other end gets what it's reaching for. NU11 can't say what happens to something that has been buried once already and gets buried again. And there's a third possibility both sides get quiet about: that the Undertone doesn't care which answer it gets. That being decoded is the whole of what it wants, and every cipher either faction cracks is the same favor done twice.

Nobody has a way to test that. So you pick the answer you can live with, and you get to work.

Pick a side

So, which will it be: answer it back, or silence it? You choose a faction when you sign on, and for now you're on it for the long haul, so pick the one that fits how you'd handle a thing like this.

One practical note before you commit: if a faction's short-handed, join that one. The smaller faction gets a bigger daily budget of moves, so the underdog isn't the charity case, it's the sharp play.

A night in it

So here's how a night actually goes.

How it works

Z3R0B3A7 is a capture-the-node game played entirely on your MeshCore mesh: slow and asynchronous, the kind you check in on a few times a day across a week, not a match you sit down and finish in one go. You play it with your MeshCore radio (long-range LoRa hardware; new to it? start at meshcore.io) by direct-messaging N3T C0NTR0L, a bot node that lives on the mesh. That DM thread is the whole interface. You message N3T C0NTR0L to do everything: engage a site, fortify it, ask for a hint. This site is just the scoreboard, a few minutes behind.

Since the whole game rides on those messages, you can play it from anywhere your radio still has a path to N3T C0NTR0L: parked on the couch, up on a ridge, or out with your buddies over a few beers, thumbing in captures between rounds. If you can reach the bot, you're in the game.

To get on, you need a MeshCore radio joined to the same mesh this board runs on (same channel and frequency; whoever runs your mesh can point you at the settings). Then it's three steps:

This board's coverage is . Not in range of that mesh? You can read along, but your radio won't reach this board's N3T C0NTR0L. Z3R0B3A7 is a self-hostable kit, though: any MeshCore community can run its own board.

1. Introduce yourself. Send an advert. N3T C0NTR0L can only message a node it's already heard from, so your advert is what drops you into its contacts, and it into yours. (If it never answers, this is almost always why.)
2. Check in. Message it radio check. It'll tell you it's got you, and how your messages are routing to it. A reply means you're through.
3. Pick your side. Message join 3ch0 or join nu11. That's your faction locked in, and you'll get your side's private channel.

That's it. You're an operator.

One thing to expect from the first message: replies come back over a slow radio mesh, so give the bot up to a minute to answer. If you don't hear back right away, wait it out. Firing the same command again just earns you a stack of duplicate replies once they all catch up.

One bit of shorthand to expect: N3T C0NTR0L calls the sites "nodes," same as every radio on the mesh does. This page says "sites" because that's what they are to you: the ground you take and hold. Same thing.

The clock and the score

The game runs in weeks called Drifts. A Drift opens on the morning of day 1 with the site grab: the whole board is neutral, and whatever a side takes that day is shielded until day 2, so the first day is for claiming ground, not fighting over it. It closes on the evening of day 7 with the Whistle, when the week is scored (the board counts it down for you).

A Cycle is the season above the week: three Drifts, then a quiet week to cool down and let the board reset before the next one. Win more Drifts than the other side and the Cycle is yours. There's a catch, though: the Undertone can win a Drift too, and its wins count for nobody. Level on Drifts, and the Cycle goes to whichever side gained more across it; level on that as well and nobody takes the Cycle: the signal took it. You pick your side once and it's locked for the whole Cycle, so the same operators hold and lose ground together week after week, and as the Cycles climb, the ciphers get harder and the Undertone gives up a little more of what it is.

Your moves are rationed. You get a daily budget called Headroom (engaging a site and fortifying one each cost a point), and it refills each day. N3T C0NTR0L shows your count. How you spend it is up to you: run as a lone operator picking your own fights, or drop into your faction's private channel and plan the week together, deciding who pushes into enemy ground, who shores up what you already hold, and when the whole side throws its Headroom at one site at once. A faction that coordinates its Headroom punches well above a scattered one.

You score by holding: every site your faction keeps earns for you, minute by minute. At the Whistle those earnings are split by how many operators on your side actually showed up (per-capita), so a small, wide-awake faction can out-score a big lazy one, and a handful of committed operators can take a week outright. Prying a site off the other side pays a bonus on top. Whoever earned the most per operator wins the Drift… unless the Undertone got greedy while everyone was looking the other way.

The forces on the map

The board isn't only you and the other side. A few things move on their own (the Undertone reaching up out of the noise, sites that light up and change the week), and you want to know them by sight before they catch you out.

• The static. Purple sites are the ones the Undertone has surfaced into and taken. Any one comes back with a single solve (the easiest ground on the board), but only if someone bothers. And there's a hard edge: if the Undertone holds a big enough share of the map when the Whistle blows, it wins the week, over both factions. It's the one thing that can make 3CH0 and NU11 stop and work the same side of the board.
• Beacons. Now and then a site lights up with a ring and a tag: tempo or edge. Holding one buffs your whole faction until the Whistle: a tempo beacon hands every operator on your side extra moves each day; an edge beacon shaves a tier off all your captures. They wake partway into the Drift. When one lights up, it's worth dropping everything to grab.
• The Spike. Late in the week the Undertone surges into a single site (the Spike; the radio announces it as AN OPENING and tags the site OPENING) and forces it to a brutal tier, dug in deep. Break the Spike off it and hold that site to the Whistle for the biggest swing on the board. The reveal is short-notice, so nobody can camp it.

What you're chasing

Every cipher you crack is yours to keep: your record follows you week to week. It's yours, not your faction's.

Your rank is how well the mesh hears you. You start out Unheard: no signal, nobody tuned to you. Solve ciphers and you climb (Faint, Carrier, Peak, Pinned) up to Zero-Beat. That top rung isn't a random word: zero-beat is the whole point, two signals tuned so perfectly against each other that both fall to nothing. An operator at Zero-Beat is someone who's been doing exactly that, over and over. Send me any time to see where you stand.

You also collect badges along the way: markers for things you did yourself, like your first solve, breaking a site off a full-height wall, or cracking a Spike. Nobody can take one from you.

Most badges have five levels (Roman numerals: Taker III, Anchor V), and each one is harder to reach than the last. The top level of anything is meant to take years, not weeks. Once you've reached a level it's yours: a badge never goes back down.

They aren't all about doing more, either. Some count range: Surveyor goes up for holding a site during a Drift, whether it's one you've never taken or one you took last week, so the far corner of the board is worth the trip. Some count staying power: Anchor counts the days your captures actually survived, added up across every site you hold, so a site nobody can pry off you beats trading the same one back and forth all afternoon. (A hold ends at the Whistle, since the board goes back to neutral for the next Drift. The days add up week after week.) And some just count showing up: Steady Hand is for being on the air five days inside one Drift. That's all on purpose, and it's how the old radio awards work too: chasing somewhere new costs no more airtime than working the same repeater again.

And if you catch the bug for the mystery itself (what the Undertone actually is, why it's here, what it's saying), that story isn't crammed onto this page on purpose. The lines operators have pulled out of the ciphers, drift by drift, collect in the Waterfall: a few ciphers a day carry a line of it instead of a radio word, and when yours does N3T C0NTR0L says so ("that answer was a line of the signal"). Go as far down as you want, or just play. The signal doesn't mind either way.

Before you sign on

One unspoken rule between operators: be decent. This runs on a real mesh, in a real community where people know each other and each other's public keys. No harassment, no doxxing, no wrecking it for everyone else. Cross that line and the mesh admin can cut your key off from N3T C0NTR0L: no bot, no game. The full house rules are on the terms of play page.

Glossary

You'll have met all of these by now. Here they are in one place.