Contents & Roadmap

A published, tracked account of what is missing. Generated from data/roadmap.json, so progress is recorded in the corpus rather than in someone's memory.

The bundler carried a hand-written list of stylesheets that had drifted from the one index.html actually loads, dropping blueprint.css. All 27 drawings rendered in the single-file edition with no hatching, no line weights and no dimension styling, while the served site was fine. The list is now read off index.html, and a guard refuses to emit a bundle that dropped a stylesheet.

Six of the eight were not missing numbers at all — they were flow arrows wearing the dimension class: the fish bouncing off a tight gill net, quicklime and water pouring during slaking, air in and exhaust out of the lime kiln. Those were reclassed rather than labelled. One was a genuine unlabelled measurement — the pole lathe's bed span — and it took its number from the build's own spec table, 1.80 m, rather than from the drawing's scale. All 67 measurements now carry a number.

Part 9 of the composting latrine is the handwashing station, and figure 2 is titled 'Tippy-tap handwashing station' — an entire figure about it, with no key on it. Part 8, urine diversion, was not drawn at all, so a key alone would have pointed at bare slab; a schematic basin and outlet were added and keyed. The gill net's selvedge and bag of slack were keyed onto the rig drawing where both features already exist. 123 of 123 parts are now called out.

Three guards added. A measurement with no number — scoped to <line class='dim'>, because <path class='dim'> is a flow arrow and counting both together cried wolf five times out of six. A part listed but never called out, which was never checked in that direction. And two callouts overlapping, which found a defect nobody had reported: the gravel and underdrain keys on the slow sand filter sat 14 px apart with 9 px radii, so one was unreadable. All three verified to fire.

Corrected to 14 builds, 27 blueprints and 17 plates, and the builds table — which listed 12 of 14 — gained the fish trap and the gill net. Then guarded: validate.mjs now reads the stated counts out of the README and compares each against the corpus, and counts the table rows, so this particular drift cannot recur.

The site described a chemical that boils on contact with water, a fishing method illegal across much of the world, and treatments written for the case where no doctor exists — with no safety notice, no medical disclaimer and no statement of the licences it carries. /policies now enumerates 12 specific hazards rather than gesturing at them, and every build page links to it above the fold.

CC BY-SA 4.0, chosen by the owner. Copy, print, mirror, translate and build on it, commercially or not, with credit, a licence link, a note of changes, and the same terms downstream. The share-alike is deliberate: a document whose premise is that you take it offline and keep it is worth very little if the copy you took cannot legally be passed on. It is also compatible with the eight CC BY-SA plates already embedded, which keep their own terms regardless.

Each build now hashes its own output and publishes the value on Take it offline, with the verification command for each platform, plus a .sha256 sidecar next to the file. The hash is published on the served site and deliberately never inside the bundle: a checksum written into a file changes the bytes it describes, so release.json is excluded from the bundle's inputs and the offline edition says plainly that it carries no hash of itself. Verified stable — two consecutive builds produce the same digest, so it is not self-referential.

Prevent deficiency disease, tier 1: counting food groups, alkali-cooked maize, parboiled rice, vitamin C through late winter, iodine inland, vitamins A and D for children, weaning and arm measurement, and the end-of-winter check. The ladder's own success creates this gap: a farming group narrows its diet to one grain.

Refrigeration and the cold chain, tier 4: stored ice, evaporative cooling, ammonia vapour compression, flame-driven absorption, the vaccine cold chain and the shake test. The antibiotics and vaccines step now requires it; before, it listed refrigeration as an input with no step that produced it.

Two steps. Boats and safe water travel, tier 1: floating and swimming first, the 1-10-1 cold-water rule, raft buoyancy worked in kilograms, the dugout and its wall gauge, outriggers, the capacity rule, weirs and strainers, and rescue from the bank. Canals and locks, tier 3: the level survey, puddled clay, the mitre-gated pound lock, the water each lockage costs, the towpath, and lock safety.

Batteries: from the voltaic pile to the lead-acid cell, tier 3: which metal pairs give what voltage, the pile, the Daniell cell, distilling zinc, a compass galvanometer, forming and charging lead-acid cells, and plating and electrolysis. The telegraph now requires it; before, it named the Daniell cell with no step that made one.

Both, deliberately. Included as organisation: keep watch and defend the settlement — the rule for force agreed in advance, a defensible core, the night watch, alarms and drills, dogs, fire, neighbours, and the refuge. Excluded: the making and use of weapons, and fighting technique, stated on the policies page.

Teeth, tier 1: sugar exposures rather than amounts, the chewing stick, children's teeth, the four signs that a tooth abscess is spreading toward the airway, rinsing and draining, replanting a knocked-out tooth, and care after extraction. Extraction technique is deliberately not taught on the page; it is learned by hand.

Done — js/plates.js is the shared photograph component for builds, guides and steps, and steps carry figures, plates and a detail procedure. All 85 steps now carry one, with a check on every entry.

An optional block per step: what the record shows was adopted here, what to do instead, and the evidence. One rule keeps it honest — the alternative must be achievable at the same tier. If it needs a higher one, it is not an alternative, it is a wish. Built as a better list on each step; the validator refuses an alternative whose needs include a later tier.

money, law, governance, settlement and science. Held to five deliberately; every further candidate folded into an existing domain rather than earning its own — education stayed in society, which already had the school step.

Seven of seven. Besides the debt record, double entry and credit, four new steps. Standard weight: the equal-arm balance tested by transposition as NIST still publishes it, weights in OIML R 111's series and tolerances (a 1 kg trade weight within ±50, ±160 or ±500 mg by class), sealed adjusting cavities, a master set never used in trade, and stamping, registers and unannounced inspection. The mint: the standard written into law, trial plates held outside the mint, milled edges against clipping, and the Trial of the Pyx, recorded since 1248, as the model of a public random-sample test; the Great Debasement of 1544–1551 as the failure. The company: incorporation by registration, limited liability paid for with disclosure, and the G20/OECD principles on shareholder rights, directors' duties, independent audit and beneficial ownership. Reserves and the price level: a consumer price index on the ILO/IMF manual, a 2 % target, an independent central bank, Basel III capital and liquidity, deposit insurance, the 2023 run on Silicon Valley Bank, and Cagan's 50 %-a-month line for hyperinflation.

Five of five: boundary and tenure; published rule with a court; the enforceable promise, with enforcement against property and never the person; the register of land, births, deaths and companies; and constraint on the ruler — divided, removable power, a bill of rights the courts enforce, and emergencies that lapse. The institutions guide maps each onto the institution that runs it.

Six of six: the first public good, with the maintenance rule that separates infrastructure from ruins; the census, with individual returns sealed; the health authority, on the record the largest life-expectancy gain of any institution; departments staffed by open competition; the front counter, with a deadline for every decision; and independent audit and statistics. The institutions guide lists every institution in founding order with the faults each is built against.

Six of six: the camp and the ground, the house plan — the fire outside the sleeping room, floor space per person, wall weight by climate, the turn to the winter sun and the eave sized by latitude — plot, street and block, with the separation of water and waste carried there as a layout decision rather than a tier-2 sanitation step that would have duplicated t4-sanitation, the fire code and zoning.

Five of five. Besides standard units, controlled comparison and priority by publication: the laboratory as an institution, on the OECD Principles of Good Laboratory Practice — written procedures, calibration traceable to national standards, raw data recorded directly and corrected without obscuring, quality assurance independent of the work, and an archive from which any study can be reconstructed — with WHO's risk-assessed biosafety and accreditation to ISO/IEC 17025 with proficiency testing; and knowing whether a result is real: random sampling from a list, margins of error (±3.1 points at 1,000), sample size fixed in advance, registration before the data arrive, the ASA's six principles on p-values, correcting for many tests, and the 2015 replication of 100 psychology studies, in which 36 % of the replications were significant against 97 % of the originals.

Three of three. Besides arithmetic for everyone: knowledge held by an institution — a self-governing charter, academic freedom and tenure as UNESCO's 1997 Recommendation defines them, programmes with stated outcomes, external examiners on every award, and review by an independent agency on the European standards; and the press, and who gets to speak — no licence to publish or to report, no punishment for criticising the government and no prison for defamation, protected sources, plural and independent media, and the record on attacks on journalists, on the UN Human Rights Committee's General Comment 34 and UNESCO's figures.

Ten, each on the step where the choice is made: lead where it can reach a mouth (glazes, sweeteners, paint), bloodletting and purging, streets only as wide as today's traffic, white phosphorus matches, lead water pipes, water supply before sewerage, combined sewers, asbestos lagging, leaded petrol and CFC refrigerants. Arsenical pigments, mercury in hatting and radium paint were dropped from the plan: no step makes those decisions, and the lesson each carries is carried by one of the ten.

Eight: keeping the latrine away from the well, oral rehydration, handwashing between patients, kangaroo mother care, citrus and greens against scurvy, alkali-cooked maize, parboiled rice, and chlorinated water. Every one needed nothing the society did not already have.

The better path gathers every item from the step it sits on, ordered by tier, and is linked from the step that states the principle, the home page, the footer and the contents.

Four drawings, each on the step where the decision is made: what each water treatment removes, the routes from faeces to the next mouth (WHO's F-diagram), the temperatures that decide the metal, and what each preservation method takes away from spoilage.

Every build carries a modern colour photograph. Closed before 2026-09-17 and not marked here until 2026-09-22.

Smithing, charcoal and lime were published on 2026-09-16 with the other field guides. Not marked here until 2026-09-22.

data/sectors.json: 12 sectors, 41 tracks, 105 levels. All 92 steps have exactly one primary home, and cross-listings are marked, so brick, lime, cement and glass now show under Shelter & Architecture as well as Materials. 25 planned cells, each with a note, and 25 options for choosing by what you have. Guides and builds attach through the steps they already serve. The validator refuses a step with no home or two homes, a track whose tiers go backwards, a guide or build homed where it serves nothing, and a planned cell whose step has already been written. Each check was broken on purpose and fired.

Explore shows the 12 sectors, each with a bar of how far up the levels it is written. A page per sector draws every track as a strip of eight levels: written steps, cross-listed steps marked with their home, planned cells hatched, empty cells left blank. A page per track climbs one level at a time, with what each step needs first, its guides, builds, sheets and books, and a chooser for five levels where the method depends on what the site has: tick clay, stone or logs and the options that fit move to the top. The navigation is five items, Explore, Ladder, How-to, Library and Ideas, plus search. Every old URL still works. Every sector and track is rendered by all three suites, and tools/width-check.mjs renders 210 pages in a real browser at 390 and 1280 px. It found guide and build pages running off a phone screen, which is now fixed (CIV-072).

Every step page opens with where it sits (Explore › sector › track › level), any subject it is cross-listed under, and one panel with everything for it: field guides, builds, reference sheets, books and its place in its track. Its pager now also steps through the track, and names a planned gap rather than skipping it. Guides and builds carry the same breadcrumb and say which steps they serve in which subjects. Ladder cards show their subject and a guide, build and sheet badge, and the ladder and the library filter by the 12 subjects, cross-listings included, so Shelter shows the brick and glass above tier 1. How-to indexes all 29 reference sheets for the first time, grouped by subject with the field guides and builds, and search now reaches guides, subjects and sheets (CIV-071).

This page now carries a coverage matrix: 12 subjects by 8 levels, each cell counting the steps written there and how many have a field guide and a build, coloured red where no step has a guide. The 25 planned cells are published below as a writing queue, ordered by harm, with every step that still has no field guide listed under it. Three new counted gaps, derived by the validator like the rest: steps with a field guide, steps with a build, and levels with a step written. The matrix, the queue order and the unguided list are checked against the data, and each check was broken on purpose and seen to fail.

The Dwellings track now climbs from the debris hut to a framed, glazed building. Two new steps, Masonry house and chimney at tier 2 and Framed and glazed building at tier 3, each with a numbered procedure, a check on every entry and colour photographs. Two new builds: the fireplace and chimney, whose throat, flue, hearth and clearances come from the USDA's Fireplaces and Chimneys and Rumford's 1796 essay, and the log house from the Forest Service's Building with Logs, which turns the log option on the material chooser from planned into a build. Six drawings, 16 new photographs, five newly verified books. Tiers 4 and 5 of the track stay published as planned cells.

One word on screen for an entry on the ladder: step. 26 uses in the data and 12 in the pages were changed; the two that mean a physical ladder stay. The validator now refuses the other word anywhere a reader can see it. The ladder and the library filter by the 12 subjects instead of the 16 domains, and old domain links still filter and say which subject replaced them. The README describes the subject map and its checks, and llms.txt opens with every subject, track and level, planned ones marked.

Where civilization stands: humanity's energy use on Sagan's continuous Kardashev scale, K = 0.731 for 2025, with its course since 1800; thirteen measures of energy, wellbeing, knowledge and sustainability from their custodian agencies; the planetary boundaries; Cook's energy-per-person stages placing each tier of the ladder on the same scale; and the horizon, milestone by milestone. tools/scale.mjs refreshes the data once a year and appends to the record. The validator recomputes K, requires a source, licence and file hash on every series, and fails when the data is more than 18 months old.

It said reaching Type I needed ten thousand times today's energy; under the formula it cited, it is about 500 times. Its four figures are now tied to the scale data (CIV-092).

Micro-organisms: about two dozen organisms that decide who lives, pathogens first, each with how it spreads, how long before illness, what kills it and the step that prevents it; the useful ones that ferment food and fix nitrogen; eight micrographs; the nomenclature registries for the complete record.

Two builds: the bead microscope, Leeuwenhoek's design, 150–350× from a melted glass bead; and the refracting telescope with lens grinding, 40× from a 1-metre objective. A glass material was added to the drawings.

All 118 elements from PubChem's data, pinned and checked. The 30 a rebuilding civilization makes or must handle carry where they come from, how they are obtained and from which tier, what they are for and how they harm; twelve carry a photograph of the ore or the element. Searchable by name and symbol.

The sciences: fourteen branches on the international classification of research fields, each with the results a civilization must keep and the free textbook for the rest, and the seven constants that define the SI. 87 of 94 steps now name the sciences they rest on.

Eight more basic guides: essential medicines, the body's numbers, poisons, calculating by hand, properties of materials, minerals and ores, soils and plant nutrition and the electromagnetic spectrum; and nineteen bright stars added to navigation. The medical ones give no doses and point to WHO and Hesperian for them.

Every source of energy, from wood and charcoal to fission and hydrogen, with storage and the whole chain to useful work: what each gives, whether it runs on demand, its figures from the IPCC, the US EIA and the US Department of Energy, and how it can hurt you. Sixteen reference sheets, each corrected in its caution band.

The site's pages and data are saved on the first visit, 2.5 MB; photographs are saved as you view them, and Take it offline saves all of them on request (CIV-083).

Settlements & Planning is its own subject. Lay out the camp sets the humanitarian minimums on the ground: 45 m² per person, 2 m between shelters, a 30 m firebreak every 300 m, latrines within 50 m of every shelter and 30 m downhill of the water, water within 500 m. Choose the ground builds above the design flood, not the remembered one, and tests water, slope, groundwater and wind. Plot, street and block gains its block plan and street section, the planning guide its first five sections, and set out a block puts a plan on the ground with cord, pegs and 3-4-5. Five drawings; seven photographs; figures from the UNHCR Emergency Handbook, FEMA and UN-Habitat.

The sustainable farming guide: FAO's three principles of conservation agriculture (no ploughing, at least 30 % cover, at least three crops), rotation with a legume, compost held at 55 °C for 15 days (US EPA), integrated pest management with icipe's push-pull, pesticide safety by WHO hazard class and the FAO/WHO Code, water efficiency by method (FAO) and trees on the farm. Three better-path items on the first farming steps, and drawings for working across the slope, a push-pull plot and an irrigation channel with its drain. Six photographs.

Both written. Fire separation and the building code: walls measured to the boundary (window area 5.6 m² at 1 m, any amount at 6 m), party walls carried 375 mm above the roof, no thatch within 6 m of a boundary or on a row, chimney outlets 600 mm above the ridge, an escape window of 0.33 m² in every upper sleeping room, exits by headcount, fire water by the NFPA 1142 formula with a 7,600 L floor, and a 3.7 m route for the pump. Zoning: a year of wind records, every trade listed by what it emits, separation distances from EPA Victoria's 2024 guideline (tannery 250 m, abattoir 500 m, rendering 1,000 m, refinery 2,000 m), works downwind and downstream, no homes in the functional floodplain and no chemical store in the 1 % flood zone, and every compatible use mixed.

Four steps take the crops track to tier 7. The four-course rotation, field drains and the seed drill: fodder roots and clover in place of bare fallow, pipe drains under 600 mm of cover with mole channels no more than 2.75 m apart, and wheat drilled about 4 cm deep at a known rate. Drip and sprinkler irrigation: FAO's application efficiencies (surface 40–50 %, sprinklers 75 %, drip 80–90 %), tensiometers read at 18–25 centibars, emitter flows within 10 %, and filters, check valves and line cleaning, with FAO's gravity family drip kit for 500 m² as the build. High-yield varieties, and the Green Revolution's bill: the semi-dwarf varieties and their package, and the costs with a rule against each — metered groundwater, banned highly hazardous pesticides, gene banks and biofortification. Sustainable intensification: conservation agriculture, a nitrogen budget kept between 50 and 90 % efficiency, alternate wetting and drying in rice, and the 13 % of food lost before retail.

Greenhouses and both remaining steps are written: cold frames, hotbeds and the glasshouse, the modern greenhouse, soilless growing — nutrient-film channels at 1.2–3.0 % fall, deep-water culture above 4 mg/L of oxygen, EC and pH by crop, and closed systems with filtered returns — and vertical farms, stated with their electricity bill of about 247 kWh per kg of lettuce dry weight against 70–211 in greenhouses. The greenhouse guide now has a part on growing without soil — the four systems by crop, EC and pH by crop, source water and closed systems — and a fourth build, the nutrient-film bench: eight 6 m channels on a 2 % fall, about 1 L/min each, a tank that holds all the solution when the pump stops, and lettuce at Cornell's 38 plants per m².

Fish ponds is written, in a new Aquaculture track: soil and site tests, a 400 m² pond with FAO's dike dimensions drawn in section, species by water temperature, lime and manure rates, the dawn oxygen check and the Secchi disc, harvest, and the two hazards that lead the step: drowning and liver flukes from raw fish. The aquaculture guide takes it from site to harvest — species by temperature, sunrise readings of oxygen, Secchi depth, pH 6.5–8.5 and alkalinity, carrying and acclimatising fingerlings, FAO's bran ration by month, daily care — and the drainable fish pond builds the 20 × 20 m pond with its levels set before any earth moves: the outlet 10 cm below the bottom, a 10–15 cm pipe with an anti-seep collar laid before the dike, a 30 × 40 cm wooden monk, and the fence before the water.

Both steps are written: plan the city before it grows — land for 20–30 years of growth, an arterial grid about 1 km apart pegged before anyone builds, a street hierarchy from 45–60 m arterials to 10–15 m local streets, utilities in common ducts and public land reserved — and the compact, connected, resilient city, built to UN-Habitat's five principles and measured by SDG 11's 500 m transit and 400 m open-space walks and the Sendai targets. The planning guide now runs from a camp to a city in twelve sections under four parts: street widths by class, public space and transport within a walk, works kept from homes by EPA Victoria's distances, England's flood zones and what each may hold, room to grow, and how a plan is published and kept.

The boats guide: design categories and lifejacket levels, capacity and freeboard (US Coast Guard, FAO), air-dry wood densities from the USDA Wood Handbook, stability, nine hull types by what they are built from, propulsion and hull speed, the collision rules and upkeep. Three builds with dimensioned drawings: the log raft, the dugout canoe with outrigger and the coracle. Boats and safe water travel gains three drawings. Eight drawings; ten photographs.

The water ladder climbs past the dugout. Plank boats, oars and sail: four ways to join planks, FAO's timber and nail rules, caulking, oars sized by the 7/25 rule, and when a boat may carry a sail, with FAO's 4.9 m flat-bottomed plank boat to build. Seagoing sailing ships: frame-first building, rigs and pointing angles, the Vasa's stability test, and scurvy. Steam, iron hulls and the load line: paddle and screw, watertight bulkheads, the 1852 boiler rules, the load line mark to the 1966 convention, and SOLAS. Modern ships and small craft: containers, the conventions, AIS and 406 MHz beacons, small-craft standards, and IMO's emission targets. Six drawings; seventeen photographs.

A new track, In the air. Kites: how a kite pulls and how hard, which kite for which wind, building by Kitecraft's rules, the bridle, line strength, where not to fly, and carrying a line across a gorge as at Niagara in 1848, with a 1.5 m line-carrying kite to build. Balloons: lift per cubic metre, hot air from the Montgolfiers, hydrogen's lift and fire risk, tethered and weather balloons, and what kills balloonists, with a tethered model balloon cut from twelve gores. The flight guide: the lift equation with a table, lighter-than-air, kites, balance, and the path to manned flight. Five drawings; nine photographs.

The air ladder reaches today. Gliders and the control problem: the Wrights' order of work — measure in a tunnel, long curved wings, balance ahead of the neutral point, three-axis control, and a glider flown as a kite before anyone rode it — with the 1902 glider as a general arrangement, a model glider and a wind tunnel to build. The powered aeroplane: the 1903 machine, power against weight, propellers as rotating wings, weight and balance, oxygen, and proven, inspected designs. Jets, helicopters and air traffic control. Modern aviation and drones: airline safety, EU and US drone rules, electric aircraft and sustainable fuel. Nine drawings; eleven photographs. Manned aircraft get general arrangements, not construction procedures.

Mathematics: 25 results in seven parts, from place value and Euclid's algorithm through Pythagoras, trigonometry, logarithms and e, the derivative, the integral, Taylor series and Newton's method, to Euler's formula, Fourier's series and transform with the FFT, Bayes, the normal distribution, least squares, Boolean algebra and Shannon's information. Every date and attribution from the MacTutor archive or Euclid's text. Formulas are MathML in a self-hosted STIX Two Math font, which only pages with formulas fetch; the validator admits only MathML Core in them.

Physics: 23 results in eight parts. Newton's laws and gravitation; work, energy, power and the pendulum; Archimedes, pressure with depth and Bernoulli; heat capacity and latent heat, Carnot's limit and the heat pump, thermal radiation; the speed of a wave, refraction and the thin lens, the limit of resolution; Ohm's law, Faraday's law and the transformer, the motor force and Maxwell's equations; special relativity and Einstein's field equations, with the GPS corrections; the photon, Schrödinger's equation, radioactive decay, fission and fusion. A closing table of what physics learned since 2000 (neutrino mass, the Higgs boson, loophole-free entanglement, gravitational waves, the 2019 SI, the black-hole image, fusion gain above one) and the open questions of dark matter and the Hubble tension, each from its primary paper.

Chemistry: 12 results in four parts. The mole, conservation of mass and Moseley's atomic number; the ideal gas law; dilution, pH and buffers; Hess's law and free energy, with the temperature at which limestone burns; equilibrium and Le Chatelier through the Haber process, and the Arrhenius rate; Faraday's laws of electrolysis and the Nernst equation. A table of the eleven reactions the ladder runs on, from burning lime to ammonia, each linked to its step, and what chemistry added since 2000: the completed periodic table, the 97 % fall in lithium-ion cell prices and metal–organic frameworks.

Astronomy: 12 results in three parts. The Gregorian calendar, the sidereal day, latitude from the noon Sun with the declination of the day, the length of the day, and longitude from time; Kepler's laws and orbital and escape speed; the solar constant, parallax, standard candles, the Doppler shift and the Hubble–Lemaître law. A closing table of what astronomy learned since 2000: over 6,000 exoplanets, Gaia's map of the galaxy, the age and contents of the universe, the black-hole images, JWST and the DART asteroid deflection, each from its primary source.

Earth sciences: 11 results in five parts. Rain on a catchment and Darcy's law, with why the 30 m latrine rule holds in sand and fails in gravel; pressure with height, the lapse rate and cloud base, and wind chill; radiometric dating and plate motion; moment magnitude and the speed of a tsunami, with the warning signs; the planet's energy balance and the forcing and warming from carbon dioxide. A closing table of what the Earth sciences learned since 2000: CO₂ at 427 ppm, 2024 the first year above 1.5 °C, the IPCC's Sixth Assessment and groundwater weighed from space.

Biology: 24 results in six parts, and the anatomy of the human body the owner asked for. Cells and energy (cell theory, Fick's diffusion, photosynthesis, respiration, Michaelis–Menten); the human body (directions and abdominal quadrants, the eleven organ systems, skeleton and spine, heart and circulation with Harvey's cardiac output and Poiseuille's law, airway, gut and kidneys with the oral rehydration formula, nerves and hormones, energy needs and BMI); microbes and defence (bacterial doubling, the D-value, immunity and vaccines); inheritance (Mendel, DNA, the genetic code, Hardy–Weinberg, effective population size, the breeder's equation); populations and epidemics (selection, logistic growth and the maximum sustainable yield, the ten-per-cent rule, R₀ and herd immunity, the SIR model); and the modern tools (PCR, sequencing, CRISPR, mRNA vaccines, AlphaFold). Homed in Health and linked from its sector page.

Engineering: 11 results in five parts. Levers, pulleys and gears, and the capstan equation; stress, strain and the safety factor, beams and Euler buckling; Darcy–Weisbach pipe friction with Reynolds and Moody, Manning's equation for channels, and water power; heat through a wall and Newton's law of cooling; proportional–integral–derivative feedback, with the arithmetic of reliability. Closes with what changed since 2000: solar power's 90 % fall in cost, cheap storage and the tallest structure.

Computer science: 13 results in four parts. Turing's machine, the full adder, the cost of algorithms and Moore's law; the sampling theorem, Shannon's channel capacity and error-correcting codes; the one-time pad, Diffie–Hellman key exchange and RSA, with the quantum threat and the 2024 post-quantum standards; Little's law, gradient descent and the transformer's attention. Closes with what changed since 2000: three-quarters of humanity online, machine learning, language models, quantum computers and post-quantum cryptography, each from its primary source.