Mowing: the mower bibleMO

MO1: lawn memory and the deck's real reach

The mower alone finishes a lawn, and the lawn remembers it.

The deck's real reach

The old trimmer-only band along every edge (0.45 m) goes. The deck's real shape decides what the blade reaches:

• The blade tip sits a few cm inside the deck (skirtMargin: ~3 cm at the sides, ~6 cm at the front). The deck collides with walls, fences, posts, raised slabs and bed edges; it can't go under a hedge.
• Edge cells (next to anything blocked, or the border) keep which of their 8×8 sample points the blade passed over: their coverage. Points under a fence or a wall aren't lawn. A cell along a fence is cut up to where the blade reaches; the rest is a fringe, a thin uncut strip drawn on the obstacle side of the cell.
• A cell counts as done at 70% coverage. Fringes are finish quality: a fussy client notices them, the trimmer takes them off (its own page, later), and they grow in lawn memory (a fence line never trimmed turns shaggy over weeks).
• Progress counts the whole mowable lawn (no excluded band). TrimEdges = edge cells with no fringe.
• Par from the grid, with a stock Classic 46 as the reference: shown in the sandbox only. Jobs keep their own par until the jobs spec decides (Jobs: from the phone call to the review).

What the lawn remembers

Every visit is built from the seed, then the remembered lawn, then the growth since. Missed strips, fringes, scars, scuffs, torn tips, stripes, feed and bare patches carry over.

• Exact, per 0.3 m cell: extra height (missed strips, tufts, fringes), scalp / scuff (brown, heals ~7 days, faster with feed (GA2); turn scuffs ~4 days), stripe (16 directions × 8 strengths) and the direction streak (0-3), torn tips (0-3, from a dull blade, gone in ~3 days), scorch, days fully brown and the usual height (GR2), smothered (clumps left, MO6b), ruts and stress days (MO6c), the edge coverage, and the lawn-health cells LawnGridCare has (feed, sown, bare; a fuel spill counts as bare) plus weeds (GA2). Laid grass (MO6a) lives only during a visit.
• Stored compressed: quantized, deflated, one small file per lawn (lawns/<save's lawnId>/), never plain JSON arrays (the pretty-printed JsonUtility save would grow to 15-50 MB). The planes and their bits are in Tech.

• A whole playthrough stays under ~2 MB. Decompress + apply: under a millisecond. Saved only for lawns you touched, written when the host leaves the lawn.
• Layout fingerprint: a hash of the LawnPlan output + grid size. On a mismatch the memory is dropped and the lawn starts fresh (no garbage beds after a generator change).
• On the next visit: a missed strip is a shaggy band, a scalp a brown scar, a fence line you never trimmed a little shaggier each week. LawnGrid.Grow builds the growth since.
• Stripes: per-cell lean angle and strength; fresh tips fade in 45 s. Between visits they fade with the regrowth: rotary stripes after ~1.5 cm (a day), roller stripes after ~4 cm (three days). How they're drawn: GR1.
• Co-op: the host sends the blob to guests when the lawn loads (1-15 KB).

Needs: SB1 · Done when: a lawn can be finished with only the mower, and next week the missed strip and the fence fringe are taller, on both instances.

MO2: surfaces and things in the grass

What the mower rolls over, and what it does about it.

Surfaces

Each cell gets a surface (GardenSurface): lawn, slab (flush / raised / sunken), gravel (pea / chippings / pebbles), bark mulch, bed soil. Surfaces come from each garden's own beds, patio and stepping stones and its seed (no job data; lawn memory fingerprints unchanged), and every garden gets some. Grass grows only on lawn and in slab joints.

• Around a tree trunk the deck can't reach the bark: a ring of fringe is left (the trimmer's), and the roots around it are the hard-hit zone.
• Stray gravel creeps ~1 m into the lawn from a gravel border or drive, thinning out (seeded). Those cells stay lawn (grass, progress). Mowing the edge by the gravel is the real danger zone: raise the blade, go slow, or leave it to the trimmer.
• Gravel lift = surface lift (pea 1.0, chippings 0.6, pebbles 0.15) × the blade's suction (standard 1.0, high-lift 1.6, mulching 0.8) × lerp(1.6, 0.4, blade height 3→10 cm). Throws per second over gravel ≈ 6 × lift. A high-lift blade set low over pea gravel is a machine gun. Each gravel strike is a TINK and a blade nick; MO3 throws them.
• Stepping stones and hidden stones: stepping stones (3.5 cm) and hidden flat stones (4-6.5 cm) wear the blade (0.05/s, ×3 when set low) while the blade is at or below them. Rocks and toy balls are debris hits (blade wear, +0.4 load); molehills add load and wear a low blade.

Hard hits

Raised slabs, pebbles, roots, proud edging, a raised drain, a rock set proud. The damage grows with blade speed (engine power, not yet bogged) and how far the blade is below the top (GardenSurfaces.Severity / Resolve, seeded rolls Salts.HardHit*):

1. a nick on every hit: blunting (sharpness −);
2. a bent blade (PartState.bent, integrity −): the mower shakes until the blade is replaced or repaired, wobbly lines, engine wear up to ×1.5. The bend stays after the job;
3. a stall: the engine dies until you pull the cord again (MO5a); with a brake clutch the clutch slips, the blade stops and the engine runs on (MO4);
4. rarely, a bent crankshaft on a full-speed hit with a heavy blade: an expensive engine repair, the mower shakes until it's fixed (a blade swap doesn't help).

No throws from a slab: a horrible SCREECH and sparks (slabs, drains, rocks, metal edging), wood chips (roots), chewed bits (plastic edging), and a jolt through the handle (rumble, the camera's kick). Roots scalp the turf along their ridge when the blade is set low.

Things in the grass

How the mower reacts to what it rolls over (which household leaves what is a jobs matter).

• Poop prints on grass fade in a day (rain washes them); on paving they stay until cleaned.
• The poop on grandma's lawn is the neighbour's dog's.

Needs: MO1 · Done when: a raised slab bends a low blade at full speed, and a fresh poop leaves prints across the patio.

MO3: what the blade throws

Throws come from geometry. The blade spins clockwise seen from above on every mower, so the skill transfers.

What strikes: every gravel strike (MO2's lift), a loose rock under the deck (the rock flies), and a stone set proud that the blade chips. How the chance of a strike grows with a low blade and speed is MO13.

The set-up comes from the mower (DeckSetup.Of(sim)): the bag, the mulch plug and tipping from the mower itself, the chute, the flap and the guard from its parts (MO4). The blade's blow leaves through the same openings (GR1): the front-right gap with a bag, the rear without, the front when tipped.

• The throw rose: each set-up throws mostly to the right, front-right to back-right, low; behind only without a bag; the left side only by ricochet. The skill: keep the glass on your left, don't pivot near windows, raise the blade over stones, and never spin the blade over gravel.
• First-pass shape (the figure's model, to tune in the sandbox): a stone struck at φ meets the rim about 32° further round; through the front gap only ~30% fit under the raised skirt (75% tipped up).
• The flight: every machine flies the same stone (ThrownStone): a real arc (seeded speed and elevation by opening), a tink and a spark off what it hits, a bounce or two. Damage only if something breakable is in the path; only the thrower's copy reports a Breakage (first hit wins). Never people or animals: they duck with a "Hey!".
• Breakables (Breakable): house windows (found once in the editor from each house model's glass faces, stored on House.windows: 7-16 panes a house, the town's houses too), greenhouse panes, gnomes, the client's car (its alarm). KSSHH / CRUNCH / WHOOP WHOOP, shards, a dark crack left in the pane.
• The bill: at cost on the job's result ("Broken by thrown stones": window $180, car $250, greenhouse pane $90, gnome $25), and a broken thing spoils a flawless job. These costs stand until the jobs spec; insurance comes later (IN1).
• The show: comic words ("TINK!", "KSSHH!", "WHOOP WHOOP" for a car alarm), sounds, and a slow-motion moment in solo when a stone heads for something breakable. The co-op replay inset and the ego quip are MO12.
• Co-op: strikes are seeded by (job, strike count, player) with Salts.Throw* (SD2); a throw is one Throw garden event (start, arc seed, outcome; first hit wins), so both machines see the same pane break.

Needs: MO2 · Done when: a bagged Classic mowing with the greenhouse on its right breaks it now and then, and never with the greenhouse on its left except by ricochet.

MO4: the workbench: a chassis with part slots

The model is the chassis: what no part changes (deck width, weight and turning, petrol / battery, push / self-propelled, discharge, roller mount, bar type, noise class, van footprint, deck openings). The slots hold parts you buy, fit, swap, wear out and look after. Models stay trade-offs because the chassis decides which parts fit.

The lineup

Ride-ons, the zero-turn, the cylinder and gang mowers belong to GA6 and GA7 (their controls are J36).

The chassis

The parts

Example builds:

What the parts do

• The catalogue (Sim/Tools/MowerParts.cs): the slots (PartSlot), the parts above and the chassis rules (Fits, Stock; the brake clutch is built into the Trekker and the Regent). PartEffects adds up what a mower's fitted parts do: suction, load, edge, power, push, bag, caking, unclog, stripe lay, openings.
• They change the mower: MowerStats.Compute(def, tool) (push, load ÷ power, bag size or none, unclog), MowerSim.Kit (suction for gravel lift, mulching, the roller's stripe lay, wet caking, a blade that holds its edge), the deck's openings for throws (MO3), the brake clutch (a hard hit slips it: the blade stops, the engine runs on), the grips (half the shake).
• The model shows them (MowerVisual.ApplyParts): engine tune / race kit, a sharp blade, bag L / XL, deck guard, scraper kit; stand-ins for the roller kit, the side chute and the rear flap. Everywhere a mower is shown: in hand, at the bench, in the garage, in the van, and the other player's.

At the bench

• Where: the Workshop station in grandma's garage; later the workshop tier's bench with a grinder (MO16).
• The bench cards: the Workshop station's "Parts" cards and the tool screen (UI/PartCards.cs): per slot what's fitted, the spares and the store's parts that fit (Fit / Buy / Take off, a tooltip each), and what the set-up adds up to (push, load, bag, suction, where it throws). Parts are ordered at the bench, not from the store's shelves: the store's spares wall keeps the other tools' spares and consumables (trimmer heads, line, hedge blades), and mower parts leave it. The 3D exploded view is MO14.
• Parts are physical, one set per mower (ToolInstance.fitted, one per slot; nothing = the chassis' stock part). Commands: BuyPartCommand (order and fit), FitPartCommand (a spare or a stock part back on), RemovePartCommand; the old part comes off and is kept (stock parts just go back). Spares are the company's (SaveData.looseParts); move parts between mowers at the bench.
• Labels are UI callouts on screen, never text in the 3D world.
• Migration from the old upgrades (which were bought once per deck size): engine levels → tune I / tune II / race kit, the blade upgrade → pro hardened blade, bag levels → bag L (XL from level 3), the tools upgrade → scraper kit, each fitted to every owned mower of that deck size (copied when several mowers share it; a part with no mower of its size waits as a spare). Deck radius levels are refunded in cash: deck width is the chassis now.
• Ride-ons take blades, engines and bag sizes only.

Needs: MO3 · Done when: grandma's Classic gets a high-lift blade, big rear wheels and a brake clutch at the bench, and mows (and throws) differently.

MO5: mower care, the bar and the levers

The machine you handle: the bar and the cord (MO5a), what goes wrong with it (MO5b), fixing it by hand (MO5c), and the height levers and transport (MO5d).

Care is hands-on, short (10-40 s), satisfying and optional: every task can be paid at the store's service desk (the mower is back the next morning). Crews' mowers are serviced at the depot. Neglect degrades gently and never strands you: the free patch-up of your last working mower stays. A part's condition stays its integrity (bent, cracked: money or a new part); care states are what you fix by hand.

Needs: MO4 · Done when: a mower neglected for ten jobs needs five pulls at every gravel crossing, and one evening at the bench fixes it.

MO5a: the bar, the cord and the throttle

The control real walk-behinds have: the bail bar you hold against the handle (MowerSim.Bar). Click squeezes it and lets it go (a toggle; hold is an option in MO8a). What letting go does depends on the chassis, which makes crossing a gravel path a small decision and makes engine care matter.

• The pull cord on every petrol mower: click or R when stopped (the bar is held to pull). A mower starts each job stopped and cold: choke it cold; on choke once warm it floods and runs rough. Pulls come from the engine model (cold, choke, a worn engine) and its care (MO5b); three good pulls always start a healthy engine. Grandma's mower is temperamental: the first pull never catches, a start takes 2-5 pulls and ends in a cough, even when it's looked after. A hard hit, a hose, a clog (a stall too) or the choke left on kill the engine until you pull it again. The ride-on keys its start.
• The blade's spin (BladeSpin): it spins up in 0.5 s and runs down on its own; the model's blade follows it. A slower blade cuts slower (clean speed), lifts less gravel and throws shorter.
• The throttle lever (petrol, one lever as on real cheap mowers; C / B): choke → fast → slow. Choke to start cold, then fast; left on choke once warm it runs rough (a weak blade) and stalls. Slow: tip speed ×0.75, so a lower clean speed, suction and throw carry ×0.7 (fewer and shorter throws), −30% fuel, lower revs and quieter (early mornings). The lever starts on fast every job (the cold start teaches the choke).
• The primer bulb on the pro chassis (Trekker, Regent) instead of a choke: C presses it while stopped (three presses start it cold; six or more flood it, and each failed pull clears one), and toggles fast / slow while running. The Volt has no lever.
• Parking the mower lets go of the bar (a cheap engine stops). The autopilot, the dev tools and the tests start it with SetBlades(true) (no cord).
• Feedback: the HUD's mower line (engine off and the lever, primer count, idling, running rough, the blade running down), banner hints after failed pulls (cold: choke it; flooding: off the choke; the primer; grandma's), the engine sound's revs and volume on slow, a cough on each failed pull, the control hints.
• Co-op: the pose's "blades on" is the blade driven (the others' model runs it down on its own), plus two flags: throttle on slow (their engine sounds lower and quieter) and a pull of the cord (a cough by their mower).

MO5b: care states, the service card and the desk

Each mower's care states live on ToolInstance.care (Sim/Tools/MowerCare.cs). A job works on a copy (MowerSim.Care) that goes back with the wear record. The blade's condition stays its edge (sharpening restores it); a part's bend stays its integrity.

• What neglect does to starting: a fouled plug the most, a dirty or oil-soaked filter, stale fuel. A neglected engine also loses "three good pulls always start it", up to four more pulls. The engine-stop bar makes this matter: every gravel crossing is a restart. The rates are tuned for ten jobs ≈ 25 engine hours ≈ five pulls a start.
• A snapped rope never strands you: each pull then winds the bare cord round the pulley (2.5 s a pull) until a new rope.
• The service card (UI/ServiceCard.cs), at the bench (the Workshop station) and on the mower's tool screen: each item with a bar, OK / Due (amber) / Urgent (red), what it's like ("31 h since the change", "fouled: misfires, many pulls", "7 sharpenings left"), and the desk's price.
• The service desk (ServiceDeskCommand), ordered from the service card (there's no desk to walk up to in the store): the prices above, or a full service of everything due. Paid at once; the mower is away until the next morning (taken out of the van, can't be loaded) and comes back by itself. It won't sharpen a bent blade or one sharpened ten times (a new blade, the existing repair, resets the count). Fuel and bearings are bench jobs only.
• The morning reminder: the service desk mails the mowers that newly need care, once each until they're looked after, and only once you've been to the store (grandma's mower starts with a dull blade on purpose).
• Old saves' mowers start fully looked after.
• Co-op: the host's state carries the care states to guests. A guest's mower wear reaches the host (ReportToolWearCommand, sent when the guest leaves the garden). The desk goes through the host like every command.

MO5c: hands-on care at the bench

A bench job (Sim/Tools/BenchJobs.cs) is a sequence of UI steps of four kinds: choice (the right way or a mistake), repeat (file strokes, taps, scrapes, turns, pumps; the last button finishes), hold (a meter fills while held, let go between the marks), wait (draining). Ten jobs: sharpen, a new blade, oil, the air filter (also the oil-in-the-filter line), the plug, stale fuel, the rope, the deck, the bearings, the belt / clutch cable. Each takes 10-40 s, in real time only (the running clock, DY1: a 30 s job is a quarter hour). Nothing happens to the mower until the job is finished. A 3D version is MO11.

Sharpening the blade:

1. Pull the plug lead. Forget it: an ego quip and grandma's note "Harold lost a fingernail that way". No injury.
2. Tip it on its side, air filter up. The filter box sits on one side of the engine, fixed per model (a stable hash of its id) and said in the step. Filter side down floods it with oil: white smoke and a hard start.
3. Undo the blade bolt with a block of wood against the blade (without it, the blade just turns).
4. File each end: strokes per end, as many as the dullness needs, keeping the ~30° bevel. Uneven strokes leave one end heavy. A file in grandma's garage; the grinder is MO16.
5. Balance it on the cone ("End A dips"): a stroke off the heavy end until it sits level, or bolt it back lopsided (engine wear ×(1 + imbalance / 2)).
6. Bolt it back and put the lead back on. ~10 sharpenings, then a new blade. A bent blade can't be sharpened straight: a bent blade or one sharpened ten times opens a new blade instead (the blade part's price).

The other jobs:

• "By hand" sits next to "Desk $" on every service card line that needs it (the Workshop bench and the mower's tool screen in the hub), disabled with the reason (no money for the spares, no fuel in the garage). The panel (UI/BenchPanel.cs) sits over the screen: the step, a live line (strokes per end, the cone, turns), the meter with its marks, what went wrong. "Put it down" or Esc stops, and everything is undone, mistakes included (forgiving: care is optional). The last screen says what it did and what the spares cost.
• BenchCareCommand: the finished job's result (the level left, the edge and the balance, mistakes, spares, the refuel) goes to the company as one command. In co-op a bench job runs locally and only its result is sent; the host books it and charges the spares. A mower at the desk can't be worked on.
• The Volt's pack stays a desk or store purchase.

MO5d: height levers and transport

Height levers (MowerParts.Levers), saved on the mower (ToolInstance.levers) and back with its wear, so whoever pushes it next finds them as left:

• Levers click in 1 cm steps, 3-10 cm. A small lean of the deck front-to-back is normal (it helps the cut). Scrolling at the handle of a per-wheel or per-axle mower says where the levers are. The HUD shows "Front-left lever 4 cm · deck 5 cm left / 6 cm right (TILTED)".
• The tilted deck: each side of the blade cuts at the average of its front and back levers. Forget one lever and the deck tilts: LawnGrid.Cut takes a slope across the deck, so the low side cuts lower (a scalped strip, uneven stripes) and the high side leaves it long (a tufty strip). Per axle only rakes the deck; central moves it all. Stones, roots and slabs meet the lowest point. The HUD's blade line turns red, a banner warns when the low side scalps, the model leans to the low side, and the service card shows it.
• Folding the handle (FoldToolCommand), at the hub's tool screen or the van tab. Folded, a push mower takes a row less of the van (Classic 2×3 → 2×2, Regent 2×4 → 2×3; ride-ons don't fold); it unfolds in the van only if the full footprint fits where it lies. It comes out at the job as it went in: folded, the bar is out of reach and the push is half speed until you hold E for 2 s to unfold it (which doesn't change its van footprint). The model's handle folds over the deck.
• On its side in the van: a petrol push mower turned to fit (rotated in the grid) rides on its side, air filter down until you turn it over (TurnInVanCommand; the van tab lists them in red). Every drive with the van (a job, the store and back; jobs on foot don't count) seeps oil into a filter-down mower's air filter: white smoke and hard starts until a new filter (MO5c), and a warning when you take it out at the job.
• Lifting into grandma's hatchback (Lifting): a mower over 20 kg is a hold on the tool screen, not a click: 1.6 s alone for a Classic, 6.4 s for a Regent, half that with a sibling holding the same mower on their screen (the hub pose's Lifting flag carries which mower; whoever finishes loads it, through the host). The van tab's list won't load a heavy mower into the car. Vans have a ramp: no lift.

MO6: lawn craft

How a good gardener mows. Each habit is rewarded by the lawn, and lawn memory makes the reward last.

Needs: MO1 · Done when: three weeks mowed the same way leave ruts, and rotating clears them.

MO6a: grass spring-back

Long grass is laid flat by the deck before the blade reaches it. That's why long grass always needs two passes.

• Who lays it: the deck's front lip rides 7 cm above the cut height. Grass taller than the lip (and than 12 cm) goes over: a chance that grows from 0 at the lip to certain 5 cm above it. So 16 cm cut at 5 cm is mostly laid, and cut at 9 cm it isn't laid at all: "a high first pass avoids it", worked out rather than a flat rule. A high-lift blade stands the grass up: ×0.4 (MowerSim.LayFlat, from the blade's suction).
• What it does: like rain-lodged grass (GR2), 40-60% of what should come off stays. The cell lies flat the way the mower went and isn't done, so progress stays honest. It stands back up after 2-5 minutes (by the cell), with a small spring overshoot in the renderer, as a tall tuft that cuts normally.
• Back over it: along the lay (within ~70°) it is still lying and the blade passes over it again (another 40-60%). Against the lay, the blade takes it all. Rain-lodged grass (GR2) met against its lay lies towards the deck, so the deck lifts it and nothing goes over.
• Dandelions: a standing stalk bends half the time whatever the height (85-95% of it stays) and pops back up in 5-20 s, right behind you.
• Drawn in the renderer: a laid tuft is drawn lying flat (74°).
• Co-op: CellSync.laid (seconds left, in 2 s steps): a copy that takes a shorter cell lies the way the cutter's copy does, and a cell cut through against the lay stands nobody's tuft back up. Never remembered.
• Feedback: a flattened sheen in the wheel lines, tufts popping up minutes later, and one line the first time a job's deck lays grass ("It's laying the long grass flat...").

MO6b: the clippings

Where the clippings go, and what they do to the lawn.

• The collection (MO4): a bag catches them; no bag (rear discharge) leaves them on the lawn behind you; a mulch plug and mulching blade leave none at all (more load, more blade wear, bad when wet); a side chute is fast with no bag, throwing clippings (and stones) right.
• Where they land: a mower with no bag (or a full one) moves each cell's clippings out by the discharge to one spot, so a light cut stays light, with a little scatter. Rear discharge lands just behind the deck (2 × deck radius
  • 0.3 m back); the side chute 1.4 m past the deck on the right (±0.35 m). A bag mower that is full spills where it stands.
• Wet grass is heavier, fills the bag faster, clumps and cakes the deck (MO5b).
• Clumps: 0.05 of grass mass on a cell (a long cut, a full bag, a cleared clog's wad), or 0.015 if they landed wet (wetness ≥ 0.5: dew, rain, a wet dip). Drawn as a taller wad.
• Clumps smother: a clump left at the end of the visit yellows the grass under it for 7 days (drawn with the dry-grass tint at 70-100%: visible but subtle), and that grass grows at half pace, like a scar. Stored in the lawn memory's spare bits (thirds of a week), so no new memory format.
• Grasscycling: thin dry clippings on lawn cells, and a mulcher's chopped mass (mulched, tracked during the visit), add feed at the end of the visit: 3 doses per unit of mass, at most 0.12 a visit. It fades over the month like any feed and stays below the feed task's band (so it never counts as a feed job done for free). So: no bag on a dry weekly cut is free feed; no bag on a wet, long cut means yellow patches.
• What counts as a mess (the result's "clippings left on the lawn"): clumps, and any clippings on a non-lawn surface (slabs, gravel, bark, soil). Thin clippings on the lawn don't count. Clippings thrown off the lawn altogether (a blocked cell or past the grid: beds, the house, the fence) are a ClippingsOut garden event every 2 s while it lasts (both machines see the spray); each counts as 3 littered cells, with one line on the first one ("The chute's throwing grass off the lawn...").
• The blower (LawnClippingsWork, next to the leaves): its jet moves 3×/s of a cell's clippings 0.6-1.5 m downwind over three cells, dry. A clump breaks up into thin clippings that feed instead of smothering, and slabs are blown clear. There's no rake (no such tool).
• Co-op: CellSync carries the wetness of the clippings, the mulched mass (the larger copy wins) and the smother days (from the host's memory). Off-lawn throws are garden events.

MO6c: the habits

Direction, overlap, turning, the one-third rule, refuelling and wet ground.

• Grain: the streak counts the axis, not the direction (back and forth along the same lines is the same habit; within 22.5° counts as the same). Mown along the same axis three visits in a row, a cell has a grain: its new stripe is laid at 70% (duller), and a pass along the grain leaves a tuft 8% of the time. Across it, nothing; the next visit across resets the streak. Rotate through four directions.
• Ruts: per cell, 0-3. A visit that keeps the grain (third time or more) grows a level on the cells the wheels rolled; a visit mown across lets them recover a level, and they grow out a level every 14 days on their own. A rut is a very faint brown (3% a level), grows 5% a level slower and pushes 4% a level slower. With 0.3 m cells and a wheel line every ~0.4 m, most cells of a lane carry a wheel line, so ruts show as broad faint bands (thin lines: MO18). Wheels: big rear wheels press half as hard (a light mower on them makes none), air tyres none (MowerPartDef.ruts).

• Wet ruts: a mower pressing 25 kg+ (the push and starter mowers and up) on soaked soil (soil moisture ≥ 0.75, rain or a wet dip; dew alone doesn't soften the ground) sinks a rut level where its wheels roll, once a cell a visit, with one warning line. Wait for the ground to dry, or use a light mower.
• Mohawks: the deck's outer 5 cm (across the direction of travel) only half cut a cell (55-75% of what should come off stays, so it isn't done), the same edge falloff as fringes. Met by an edge band again from another pass, it's cut. Overlapping by 5 cm+ never leaves one; a gap does. Only on real passes (the mower's frames), not single cuts.
• The wheel track guide: while mowing, the wheels leave pale 5 cm lines on cut lawn for 60 s (narrowing away over the last 20). Overlap by a wheel (10-15% of the deck). Cosmetic, drawn on every machine from the mowers it sees (WheelTracks).

• The headland and turn scuffs: laps round the edge first give room to turn and crisp stripe ends. Turning on the spot (90°/s+, under 0.35 m/s) with the deck down scuffs under all four wheels (heals ~4 days); tipped back onto the rear wheels (right click) it pivots clean, unless the soil is soaked (then the rear wheels scuff), but tipping opens the front of the deck (MO3). One line the first time. Scuffs only mark lawn cells.
• The one-third rule, at game scale: real lawn lore says never take more than a third of the height in one cut, or the lawn yellows. The game's grass grows about three times faster than in life (~8 cm a week), so a literal third would fire on every weekly visit. The line is two thirds of the height in one cut (2 days of yellow; over 80%: 4 days). A weekly cut at 5 cm (13 → 5) is fine; a fortnight's growth or an overgrown lawn isn't, unless a high pass comes first (one brutal cut, a high pass then the real height, or two visits). Stressed grass is drawn with the dry tint (55-85%) and grows ×0.75 while it lasts. Stored per cell in lawn memory; GA2 folds it into lawn health. One line after 6 such cells.
• The fuel can: refuelling by pushing the mower to the van stays (the drive: safe). With the mower parked in the garden, take the can from the van (E), hold E at the mower and let go when it's full: it pours at 0.5 L/s (the tank gauge is the hold bar); holding on overflows, and a slope (over ~6°) dribbles 0.08 L from the start. Spilt fuel on the lawn marks the cells dark and they come back bare (dead) next visit; on paving inside the garden it's a stain (an incident); off the garden's grid (the drive, the road) nothing. The van's fuel is booked once, on letting go. Petrol only (packs: MO15). The can shows as a red box in your hand.
• Results: dead lawn cells cost $3 each, a stain $8; both are rows on the results and both break "flawless".
• Speed: too fast leaves tufts and bogs the engine (the clean pace, in Tech).
• Lawn memory format 4: a habits plane (rut 2 bits, stress days 3 bits, 3 spare); spilt fuel writes the bare bit.
• Co-op: CellSync carries rut, stress, the heaviest wheel (kg), the edge band mark (with the cut that made it) and the spilt fuel; the spill is a FuelSpill garden event (both see it; the stain is recorded once). Grain comes from the lawn memory both machines load.