Abstract—Crabminer is a city builder played on the sea floor. The player runs a crew of robot crabs that turns buried metal into money. Scouts flag deposits, drills dig them up (and sometimes come up dry), and haulers, crushers, and smelters carry the ore through a pile, a press, and a lava cave until it is refined metal on a stockpile. A riser sells that metal at the surface. Things break. Drill bits snap, energy bots wear out, and any crab can lose a leg. Repair bots and maintenance bots forge replacement parts in the lava from the line's own ingots and bars. Crabs that work without rest tire and break down more, so the player chooses between all hands, A and B shifts, and three-shift relief, and must keep every job covered in every part of the day. Steady deliveries earn a flow bonus and bank overclock, a burst of speed the player can spend. Research unlocks sixteen worker upgrades. The line's buildings stand on movable plots, and energy bots refuel at a post on an extension cord that they drag to where the work is. A thermal vent lifts crabs up the lava column, and they swim down and sideways to their work. The sea joins in: tides wash nodules up and bury flags, storms stir the dunes, the lava surges, an octopus raids the ore pile, a moray eel makes haulers drop their load, rich deposits hide pearls, cargo ships post orders, and whales pass overhead. The crabs talk in emoji sentences, pull more than fifty animations, and dance with idle neighbours, which recharges them and earns a fresh start the next morning. This paper sets out the rules and reviews the economy using the deterministic simulation the page itself runs.

Index Terms—Bottleneck, city builder, game economy, maintenance, serious games, shift work, stigmergy, swarm robotics.

I. The Game

The game opens on three layers of dunes, cut from paper and stacked one behind another. The front dune holds the processing line: an ore pile, a crushing yard, a bar stack, a stockpile of refined metal, and the collector at the foot of the riser. A basalt outcrop on the right holds a pool of lava. Beside it stand a Stirling engine and the energy bots' base station, and above it a thermal vent sends warm water and bubbles up to near the surface. The middle and back dunes start out roped off. They hold richer deposits, and the player can buy the claims to them.

The player starts with nine crabs, room in the den for ten, and 120 credits. The aim is to earn money by selling metal upward. Lifetime earnings set the player's rank, and each new rank pays a bonus of a tenth of its threshold. The ranks are Pebble Boss at 150 credits, Nodule Baron at 400, Ingot Magnate at 1,000, Lava Lord at 2,500, and Crab Tycoon at 6,000. Reaching Crab Tycoon wins the game, and the time taken is the player's score. Play can continue afterwards. The game saves itself in the browser every ten seconds and whenever the page is hidden or closed, so a reload carries on where it stopped; New game in the introduction starts over.

The Crew tab hires and retires crabs and sets the shift pattern. Each further crab of a role costs 15% of the base price more than the one before, and a retired crab refunds half of what it cost. The Build tab buys upgrades. The top bar shows the day and shift, the flow bonus, and the overclock button, and it sets how many ingots to hold back from sale. The Ledger tab holds the analysis. An advisor names the slowest stage, or the job nobody covers on some shift, in plain words.

Named crabs and veterans. Every crab has a name and a record of its jobs, backup trips, pearls, sunken chests, vent rides, dances, and lost legs, shown when it is clicked and in a crew table in the Ledger. A crab that does enough of its own job earns a star, up to three, at roughly 6, 18, and 36 minutes of steady work. Each star makes it 5% faster at its own job, working and walking, but not at the backup job. Retiring always takes the newest crab of a kind, so a stable crew keeps its veterans.

Big field. The game opens straight into play, on the big field. The front dune fills the lower half of the screen, and the world is wider than the window, so it scrolls sideways. The panel floats on the field as a sheet of paper with five tabs: Crew, Build, Tech, Ledger, and View. View tucks the rest away and leaves a slider for scrolling the field. The Big field button (or the B key) switches to a side panel instead, and the ? button brings up the introduction.

Drill bits. Every hole carries a 4.5% chance of breaking the bit. A drill with a broken bit keeps working, badly. Its holes take 60% longer, it strikes 40% less often, and while it drills it draws three times its usual power. Hardened bits cut the chance to 2.5%, then 1.2%.

Energy bots. Every charge an energy bot hands over carries a 3% chance of wearing it out. A worn bot moves at under half speed and takes twice as long over each charge.

Legs. Any crab can lose a leg while it works, energy bots and the repair crews included. The base rate is about one leg per crab per hour of work, and wear raises it (Section IV). A crab with a leg missing limps at 55% of its walking speed, and the leg lies on the sand where it fell until a maintenance bot fits a new one.

The forge. Every part is made in the lava. A repair bot takes an ingot off the stockpile, and a maintenance bot takes a bar off the bar stack. Each carries its metal to the lava's edge and holds it in the heat for 1.4 seconds until it becomes a bit or a leg, then takes the part to the crab. Repairs therefore cost product twice over: the ingot is never sold, and the bar is never smelted. A stockpile reserve keeps ingots back for repairs. Bars have no reserve, so maintenance competes with the smelters for them.

Wear. Each crab counts the seconds it has worked without a break. The first four minutes cost nothing. After that, every five more minutes add up to double the breakdown chances (bits, cells, and legs) and slow the crab by up to a fifth. Standing idle wears off a second each second. Sleeping wears off four, and it recharges the battery for free at about 3% a second.

The clock. A day lasts three simulated minutes, and it is 24 hours of crab time, so an hour passes every 7.5 seconds. The game starts at dawn, 06:00. Night runs from 20:00 to 06:00. A crab can work at night, but at half speed unless it slept or danced within the last four hours, or stands in a patch of glowing plankton (see Plankton light). Scouts are the exception: they like the dark and work nights at full speed.

The workday. The player picks a pattern in the Crew tab, and a 24-hour timeline shows who is on duty when. All hands: everyone works around the clock. 8-hour day: everyone works 08:00 to 16:00 and rests the rest. Two 8-hour shifts: 05:00 to 13:00, a 3-hour rest, then 16:00 to 24:00. A and B shifts: everyone works 06:00 to 18:00. At night half of each role sleeps, a different half each night, while repair and maintenance bots work on 30% faster, untroubled by the dark. That is the night repair crew, and sleeping crabs make easy patients because they hold still. Three-shift relief: 06:00 to 14:00, 14:00 to 22:00 and 22:00 to 06:00, and each crab sleeps through one of the three. Custom: the player sets the start hour, the shift length (2 to 12 hours), one or two shifts a day, the rest between them, and one to three groups whose shifts start in turn, evenly spread through the day. Under the 8-hour, two-8s and custom patterns, scouts take the night by default. Crabs finish the task in hand before they go to sleep.

Friends. Two crabs standing idle side by side, a crusher waiting for ore beside a smelter waiting for bars, for example, pair up and dance. Dancing recharges them a little (1.2% a second) and clears their wear at two seconds a second. These are the clean thoughts. At dawn, every crab that slept or danced for at least 20 seconds the day before starts fresh, 25% faster for the first 90 seconds of the new day.

The den. The crabs' den is a round house on the first plot. Idle time is not wasted. Every five crab-minutes of standing about, counted across the crew, turns into a decoration for the den, made by the idle crab nearest to it. Most are everyday crafts: a shell garland, a sea-glass mosaic, a pebble cairn, a kelp wreath, a coral sculpture, a sand castle, a nodule totem. A big moment inspires something special: a trophy after a rank-up, a pearl lamp after a pearl, an octopus-ink painting after a shoo, a driftwood sculpture after a storm, a ship in a bottle after a filled order, and a lava lamp after a surge. Each decoration adds a point to the morning bonus and three seconds to it, and makes dancing recharge 5% faster. The den holds four, and each den upgrade makes room for two more.

The backup job. No crab stands idle while there is work on the sand. When its own job is stuck, a crab carries nodules to the ore pile instead, at its own walking pace. That means a drill crab whose bit is broken (it keeps working while it waits for the repair bot), a drill when the sand is littered, a scout when its flags are all standing, a crusher with no ore, a smelter with no bars, and an energy, repair, or maintenance bot with nothing to do. It goes back to its own job as soon as there is one, after delivering whatever it is carrying. So hauling is everyone's second trade, and a slow crusher on the backup job is a slow hauler.

Coverage. A role with one crab disappears whenever that crab sleeps, and the line stops at that stage. The ledger lays out how many crabs of each role are on duty in each part of the day. The advisor names the first gap it finds, for example "nobody covers smelter crab work in shift 3". This enforces the rule of thumb any round-the-clock plant uses: at least one worker able to do every job on every shift.

Income. The riser sends one ingot to the surface every 3 seconds while the stockpile holds more than the reserve. Riser pump upgrades shorten that to 1.8 and then 1.0 seconds. Each ingot fetches the current metal price. The price centres on 12 credits. A slow swell, a faster ripple, and a seeded random walk move it between 6.6 and 18.

Flow. A delivery that follows the last one within 6 seconds keeps the flow going, and each one in a row adds 2% to the price, up to 40% for 20 in a row. A gap resets the flow. Steady production pays more than the same metal in bursts, which rewards a balanced line over a lopsided one.

Overclock. Every delivery banks 0.6 seconds of overclock, more while the flow runs, up to 30 seconds. The player spends it with the ⚡ button (or the O key). While it runs, the whole crew moves and works 50% faster, but uses 60% more power and wears twice as fast. It is best spent while the crew is fresh and the engine has charge to spare.

Spending. Credits buy crabs and upgrades (Table II). Repairs are paid in metal. There is no upkeep.

Plots and the post. Seven buildings stand on seven plots along the front dune, from 560 to 818: the crabs' den, the workshop, ore pile, crushing yard, bar stack, stockpile, and the riser's collector. By default they run right to left from the lava in the order the metal flows, with the den at the field's edge. In the Build tab's arrange mode the plots show as paper tiles, and any building can be picked up and set on another plot, swapping with whatever is there. Moving the stockpile nearer the lava, for example, shortens every smelter's walk. The tiles are hidden the rest of the time, so the sand stays sand. The refuel post stands at the end of a 520-unit extension cord from the Stirling engine's outlet. The player can put it anywhere along the front dune. Otherwise the energy bots drag it, every 25 seconds or so, toward the middle of the crew. The post also has a home, which is wherever it was last set down. The tide's current pushes it along the sand, one way on the rising tide and the other on the falling one, at up to 3 units a second near high and low water and three times that in a storm. Once it has slipped 40 units from home, an energy bot goes to drag it back: an idle bot, a bot that has just refuelled at it, or, if it has drifted three times that far, the next bot free from charging. A pinned post goes back to its home, and a free one to the middle of the crew. Bots plugged in or parked at the post follow it as it slides. In tests, a pinned post never strayed more than about 80 units and was out of place for under a seventh of the time.

Getting about. The track is 1,000 units long. The field runs from 20 to 540, and the plots fill the stretch from 560 to the Stirling engine at 852, beside the lava at 888. A crab climbing over the lip from one dune to the next goes at half speed. Crossing from the back crest to the front of the dunes costs as much as 300 units of track. Each kind walks at its own pace. Slowest to fastest: crushers 45 units a second, smelters 52, drills 56, repair bots 60, maintenance bots 64, haulers 68 (88 with spring legs), scouts 78, and energy bots 95. A crab on the lava side of the line with a long trip to the left can instead step into the thermal vent. It floats up with the bubbles into the top tenth of the sea, which takes about 1.8 seconds, and then swims down and sideways at 200 units a second, landing on its target. Each crab checks the time both ways and only rides when riding is at least 10% quicker. Short trips are always walked.

Tides. The sea rises and falls on a four-minute cycle, and the surface moves with it. Through the highest quarter of the cycle, every 12 seconds the current washes one or two nodules up somewhere on the claimed dunes, free for the haulers. Through the lowest quarter, every 20 seconds there is an even chance that the shifting sand buries one flag nobody is working. A tide marker in the top bar says which way it is running.

Storms. Five minutes in, and every six to nine minutes after each one ends, a storm blows through for 40 seconds, with a warning 20 seconds ahead. The water darkens, the surface heaves, rain streaks the top of the sea, lightning flashes, and the ship at the top of the riser rocks. Crabs walk at 85% speed against the current, and the riser sends ingots at half speed. Every 8 seconds the storm has a 60% chance to bury a flag nobody is working. But every 4 seconds the waves stir two or three nodules up out of the sand, so a storm is a windfall for a crew with haulers to spare.

Lava surges. Just over three minutes in, and every five to eight minutes after each one ends, the lava swells for 30 seconds and throws out burning blobs. Smelting and forging take half the time, the Stirling engine makes double charge, and the vent lifts crabs faster. The advisor suggests spending banked overclock then, because the slowest stage of many lines, the lava, is briefly twice as fast.

Ship orders. Two and a half minutes in, and every three to five minutes after each order closes, a cargo ship sails in over the riser and posts an order. It asks for a little more than the line has been making, 15% over the last minute's rate across a 100-second deadline, between 5 and 40 ingots. Each ingot sent up while the order is open pays a 30% premium. Filling the order pays a bonus of 6 credits an ingot and adds a star of reputation, up to five. Each star adds 5 points to later premiums and 10% to later bonuses. Missing the deadline costs a star. In tests over half an hour, a line left alone filled about 40% of its orders. Dropping the stockpile reserve and spending overclock while an order was open filled nearly half and earned more. Orders added about a sixth to revenue.

The rival crew. From Ingot Magnate on, a crew of lobsters behind the basalt ridge races the player for every order. For each order it sets a pace that would fill the order in 75% to 120% of the deadline, divided by its drive. Its count shows beside the player's, and its ingots rise up a red line from behind the ridge to the ship's stern. If it fills the order first, the ship sails with its metal, and the player loses a star of reputation as for a missed order. Each order the player wins raises the rival's drive by 8%, and each it wins lowers it by 6%, so a strong line meets a hungrier rival and a struggling one gets some room. Over eight seeds the automatic player lost 18 of 58 orders to the rival on all hands, 10 of 60 with A and B shifts and overclock, and 5 of 64 with research. Most of what it took were orders a slow line would have missed anyway, so time to Crab Tycoon and earnings by minute 40 moved by less than 2%. The rival adds a race to the late game rather than a tax on it.

The hermit-crab trader. Four minutes in, and every four to six minutes after each visit, a hermit crab walks in from the left with a striped market stall on its shell. It keeps shop beside the den for a minute and offers three goods out of six, paid in bars or ingots taken straight off the piles. Spare drill bits or spare legs (two for a bar) let the repair crews skip the walk to the stockpile and the forge. A treasure map (two ingots) plants three rich flags on the claimed dunes. A crate of cells (one ingot) fills the engine and every energy bot. A gold gear (three bars) gives the whole crew the morning bonus at once. A lucky shell (four bars) guarantees a pearl on the next rich strike. The trade is metal for time, and it pays best when a pile is full and the line is waiting on something else.

The sea turtle. Three minutes in, and every two and a half to four and a half minutes after that, a sea turtle swims across the dunes at 85 units a second. It comes in from the side the travelling crabs are heading away from, dips to pick up one crab with at least 160 units to go its way (a flat or limping crab first), and can turn back once for a passenger it has just passed. It sets the crab down where it was going. In half-hour tests it gave four to eight lifts.

Whales. Every two to four minutes a whale glides through the open water, singing. Its shadow sweeps across the dunes, and the crabs beneath it look up and wave. The whale has no effect on the economy.

Plankton light. Three patches of glowing plankton lie on the sand, one on each dune. They creep to the right and the tide sweeps them to and fro, so over a few days each one passes the field, the plots and the lava cave. At night a tired crab inside a patch sees its way and works at full speed, and its lamp turns blue-green. A patch is 30 units across when the sea is quiet. Storms, and every ship that comes or goes, feed a bloom that doubles that, and it ebbs back over a few minutes. Over ten seeds the patches move the figures in Tables I to III by a few percent either way, about as much as changing the seed. They are a nudge toward working nights, not a reason to.

The octopus. About a minute and a half in, and every two to three minutes after that, an octopus creeps in from the left. It makes for the ore pile, or, if the pile is empty, for the nodule on the sand nearest the line. It says 🐙🪨❓ as it comes. If a crab is standing within 28 units of its target when it gets there, it flees in a cloud of ink. Otherwise it spends a second and a half grabbing up to two nodules and escapes the way it came. The player can click it, or press Shoo the octopus, at any time to shoo it off. If it is already carrying loot, it drops the loot on the sand. Unguarded, it takes about 15 nodules in half an hour, roughly seven ingots. That is less a drain than a reason to watch the field.

The moray eel. A moray eel lives in a crack between two stones on the front dune, right in the haulers' way from the field to the ore pile. Five and a half minutes in, and every three to five minutes after it goes back in, it comes out for a minute. It snaps at any crab that carries nodules within 34 units of the crack, at most once every four seconds, and the crab drops its whole load on the sand. While the eel is out the haulers leave the nodules within its reach alone, and they fetch them once it has gone. Nothing is lost but time: in twenty minutes the starting crew drops 13 to 33 nodules this way, out of about 175 stacked. Clicking it, or pressing Shoo the eel, sends it back into its crack early.

Pearls. A strike on a flag of richness 0.75 or more turns up a pearl one time in 25. A pearl is a jackpot paid in credits straight away: 60 on the front dune, 90 on the middle, and 130 on the back. It counts toward rank, and the pearl floats up the riser to fanfare. Over half an hour with all three dunes claimed, a mid-sized crew found four or five pearls worth 390 to 540 credits. That is a fair reward for scouting deep and drilling rich.

Sunken chests. One deposit in about seventeen flagged on the back dune turns out to be a sunken chest. It sits half buried with a glint under its lid, and drill crabs go for it before any flag. The first hole into it breaks it open, whatever the state of the bit: 150 to 250 credits straight away, which count toward rank, and one of the trader's goods at random, free. Over half an hour with all three dunes claimed, a crew with two scouts and two extra drills opened between none and four, about two on average. Like pearls, chests reward claiming the back dune.

The Tech tab holds five technologies. Each one unlocks the worker upgrades for one or two roles (Table IV). A worker upgrade is bought once and fits every crab of its kind, present and future. The cheapest path is the Sonar lab at 150 credits, and four of its six scout upgrades are about the night and cost 80 to 120. The full set of five technologies and twenty upgrades costs 4,450.

A night of scouting. With the night upgrades, a single scout working nights leaves the drills a field of flags each morning. With an 18-crab crew on two 8-hour shifts, the flags standing at dawn rose from about 7 to about 14, and output rose from 6.2 to 9.0 ingots a minute. Without the flag bundle, night scouts stop at eight flags and the drills run dry by midday. On an 8-hour day, putting the scouts on the day shift then does better (6.6 against 4.4). The advisor says so when it happens.

Crab talk. Crabs speak in short emoji sentences with a fixed grammar: a thing, then a verb, then sometimes who or a feeling. The things are 🔋 charge, 🦵 leg, ⛏️ drill bit, 🪨 nodule, 🧱 bar, 🪙 ingot, 🚩 flag, 🔥 forge, 🌋 vent, 🌊 tide, 🐙 octopus, 🦪 pearl, and 🦀 for you or me. The verbs are ❓ I need, 👍 on my way, ➡️ bringing it, ✅ got it or done, 💔 broke, ⛔ full, ❗ found one, and ❤️ thanks. A crab with a flat battery says 🔋❓. The energy bot that picks it answers 🔋➡️🦀, and the crab says 🔋✅❤️ when it is charged. A crab that loses a leg says 🦵💔😭. The maintenance bot answers 🦵👍, says 🧱➡️🔥 on its way to the forge, and arrives with 🦵➡️🦀. Crabs that are stuck say why: 🪨⛔ at a full ore pile, 🧱❓ at an empty bar stack, 🔥❓ at a post the engine cannot feed. On a device without colour emoji the crabs spell the words instead.

The repertoire. Crabs have 52 animations, each a pose of eyes, mouth, claws, legs, a tilt of the whole body, and sometimes a prop. There are 14 celebrations (fist pump, clap, spin, jazz hands, cheer, shimmy, moonwalk, head-bang, the robot, floss, disco, eye twirl, happy hop, and the crab rave). There are 9 social moves (wave, high-five, sway, hug, salsa, do-si-do, cheek to cheek, conga, bow). There are 13 idle routines (foot tap, looking around, yawn and stretch, eye-roll, folded arms, sigh, whistling, juggling a pebble, side stretch, sitting down, peekaboo, blowing bubbles, a sneeze). And there are 16 moods (determined, struggling, flexing, thinking, stomping, slumping, shivering, dizzy, relief, ouch, shock, shrug, salute, a sleepy nod, sparkle eyes, grumbling). About 60 triggers choose among them. These include every event in the economy, from a strike or a dry hole to a fix, a charge, a sale, a flow streak, a rise in price, research, a new hire, a crab leaving, and a building moved. They also include states such as a flat battery, a heavy load, a limp, overclock, and wear, and the length of a wait: the longer a crab waits, the sillier it gets. On a rank-up the whole crew does the crab rave for five seconds under confetti. Everyone waves their claws one way while side-stepping the other, back and forth.

The review was run in Node.js on the same simulation script the page runs. It steps in fixed sixtieths of a second with its own seeded random numbers, so a given crew, shift pattern, and seed always give the same result. Figures are ingots sold per minute, averaged over two to four seeds. The balance runs are kept with the game's source, beside a fuzzer and browser checks.

Workday patterns compared. Table III compares the patterns over twenty minutes, averaged over three seeds. A and B shifts lead at every crew size. They work the whole day but rest everyone through part of every night, so few crabs work the dark tired. All hands comes second or third. Its crabs never sleep, so through the ten night hours most of them work at half speed, and wear piles up. The 8-hour day and two 8-hour shifts trade output for rest: they are gentle patterns, best with night scouts and, for two 8s, a crew big enough to cover both shifts. Over a short session all hands still leads. The starting crew sells 3.8 ingots a minute on all hands over five minutes against 3.5 on A and B. By ten minutes A and B is ahead, 3.7 to 3.1, and by twenty, 3.6 to 2.5.

Rest pays. Dancing and the morning bonus were measured by switching them off for an 18-crab crew over twenty minutes. They add 12% on all hands (7.5 against 6.7 ingots a minute), 24% on A and B shifts (10.4 against 8.4), and little on three-shift relief (8.2 against 8.0), whose crabs are rested anyway. A first version with a smaller morning bonus (15% for one minute) made no measurable difference, so it was raised to 25% for 90 seconds.

Working configurations. Hill-climbing, moving one crab between roles at a time and averaging two seeds, found these crews. With ten crabs on all hands over eight minutes, the best was one scout, one drill, one hauler, one crusher, three smelters, one energy bot, and two repair bots, at 6.2 ingots a minute. That is only a little ahead of the starting crew plus a smelter. Over twenty minutes, the best ten-crab crew had no haulers at all: 2 scouts, 2 drills, 1 crusher, 2 smelters, 1 energy bot, 1 repair bot, and 1 maintenance bot, at 4.9. The backup job does the hauling, because every crab carries nodules whenever its own work is stuck. Dedicated haulers come back into their own as the line grows. With 18 crabs on A and B shifts the best was 3 scouts, 3 drills, 3 haulers, 2 crushers, 3 smelters, 2 energy bots, 1 repair bot, and 1 maintenance bot, at 12.7. With 30 crabs and every upgrade it was 3, 7, 5, 3, 6, 3, 2, and 1, at 28.1.

Pace. These runs were made before crabs earned veteran stars; the next paragraph measures what veterans change. An automatic player that fixes the advisor's bottleneck, fills shift gaps, and spends spare money on upgrades was run three times for each strategy. Staying on all hands without overclock, it reached Pebble Boss at 1.8 minutes, Nodule Baron at 4.0, Ingot Magnate at 8.1, Lava Lord at 17.2, and Crab Tycoon at 34.7, and earned 7,700 credits in 40 minutes. Switching to A and B shifts at 14 crabs, with overclock, reached Lava Lord at 14.4 and Crab Tycoon at 24.4, and earned 17,500. That is about six minutes of real time at 4× speed. Three-shift relief from 18 crabs reached Crab Tycoon at 26.8. Adding research to the A and B strategy delays Crab Tycoon to 28.1 minutes, because the money goes into labs first. It pays back by the end: 53 ingots a minute and 20,400 credits by minute 40, against 42 and 17,500 without it.

Veterans. A rebuilt automatic player of the same kind was run over six seeds with veteran stars on and off. Stars come early: by minute 40 almost every crab has at least one. They change little in the first ranks and help most later. With A and B shifts and overclock, Crab Tycoon came at 28.1 minutes instead of 30.9, and earnings by minute 40 rose by a quarter. With research it came at 24.3 instead of 26.0. Under three-shift relief Tycoon came about a minute later, at 31.2, but output at minute 40 was 56 ingots a minute against 44. On all hands, earnings by minute 40 rose by 6%. With fixed crews, output over 40 minutes rose by 13%.

The vent. For an 18-crab crew the vent carries a few rides a minute, mostly energy bots and repair crews heading back to the field, and raises output by about 4%. It earns its place more as spectacle than as economics, and the crabs only take it when it saves time.

Changes made in review. The first version of wear grew without limit, and a crew on all hands spiralled into breakdowns. Wear now does nothing for four minutes and at most doubles breakdowns and slows a crab by a fifth. A and B shifts at first left half of each crew working day and night, so the resting half now alternates night by night. All hands also showed night shading and sleepy faces, though nobody sleeps in that mode. The shading now only falls when there are shifts, and a crab with a flat battery looks exhausted and asks for charge rather than dozing.

No crab knows the plan. Each one runs the rule in Table I, and each rule reads only local facts: the nearest nodule, the best flag, the height of a pile, the level of a battery, whether the vent is quicker. The piles and the flags do the coordinating. This is stigmergy, the name Grassé gave to coordination through traces left in a shared workplace [1], and it is a founding idea of swarm intelligence [2]. Insect colonies divide work by giving each worker a threshold for each task [3], and robots have been built to share foraging in the same way [4]. Here the player acts as the threshold, moving crabs to whichever stage is short and choosing who rests when. The line can deliver no faster than its slowest stage [5], and the Ledger tab exists to show which stage that is.

The nodules are real. Polymetallic nodules lie on abyssal plains and consist mainly of manganese and iron oxides, with nickel, copper, and cobalt in smaller amounts [6]. Lava erupts on the sea floor too, and basaltic lava is roughly 1,100 to 1,200 °C. Octopuses are real, clever, and known to raid traps and tanks for food, though not, so far, for manganese. Pearls grow in molluscs, not in nodule fields. Tides reach the deep floor only as slow currents, and storms do not reach it at all, though deep currents can be strong. Submarine eruptions do pulse. Hot water rising from the sea floor is real as well: hydrothermal vents send up plumes of warm, buoyant water. A Stirling engine runs on a temperature difference rather than on fuel, so one placed between lava and cold seawater is at least sound in principle.

The smelting and the forging are game rules. Copper melts at 1,085 °C, which basaltic lava can reach. Manganese melts at 1,246 °C and nickel at 1,455 °C, which it cannot, and turning an oxide ore into metal needs a reducing agent as well as heat. Vent plumes rise slowly, so a crab could not ride one to near the surface in two seconds. Sunlight does not reach a floor this deep, and the night shift is lit only by the crabs' lamps. The model is faithful about the economics: breakdowns tax output, repairs consume product, tired workers break more, and the slowest stage sets the pace.

Eight local rules, three piles, a stockpile, and a refuel post make a production line that looks managed and is not. Uncertain mining, breakdowns paid for in the line's own metal, wear that only rest removes, and a price that rewards steady flow turn it into a game with real decisions. The review finds that the economy works: every role pays for itself, every upgrade raises output, shifts beat working flat out over any real length of game, and a sensible player reaches Crab Tycoon in under half an hour of simulated time. The lesson is the old one with a night shift added: find the stage that sets the pace and feed it, keep every job covered around the clock, and let the crew sleep and dance.