LANTERNHOLD — Game Design Document

Status: Iteration 1 first draft. Numbers marked [UNSIM] are hand-derived and not yet proven by a simulation in docs/sims/. Per the rubric, unproven balance or emergence claims do not count toward the score until a sim backs them. Canonical palette: docs/art/palette.hex. Art direction lives in ART_BIBLE.md; this document references it but doesn't repeat it.

1. Pitch

You keep a small floating island drifting through an endless night. There's a warm house, a hearth, a pond where wisps rise, a lantern tree, and a cat named Wick. Below the grass is soil, then the bones of earlier keepers, then the crystal that holds the island up, then roots that move at night, then the thing the roots grow from.

You research what the world is made of, then build machines so you no longer have to do the chores yourself. Every machine leaks flux. Flux sinks into the soil, rides the rain and pools in low caverns, and it calls the things that live in the dark. They never attack. They take, rearrange and whisper. Your only wall is light. The crystal that powers your deepest lamps is the same crystal that keeps the island floating.

One line: a cozy-dread automation game where every machine you build brings the dark a little closer.

Genre: 2D side-view simulation/automation, building and digging (Terraria-style cross-section), no combat. Session target: 15–20 hours to a first ending, then endless play. Audience: players of Thaumcraft, Create, Factorio, Noita, Caves of Qud, Dwarf Fortress, Against the Storm and Outer Wilds.

2. Design pillars

3. Core loops

Moment to moment (seconds): dig, place and wire. Carry light into a new dark pocket, watch a lamp stutter as it strains against flux, catch a wisp, check whether that shape at the edge of the light is real.

Per session (one Night = 24 min, typically 2–4 Nights per sitting):

1. Survey: read the night's state. Where is flux pooling, which lamps are strained, did anything get taken or rearranged, what's the weather?
2. Research: distill new items, run tests, update the Ledger, identify a compound.
3. Build: turn the most annoying chore into a machine and extend logistics.
4. Defend: re-light, re-route and vent or capture the flux the new machine leaks.
5. Descend: push one shaft deeper and carry light down it.
6. Rest: sleep at the hearth (clears temporary warp) or work through the Deep-watch for its rewards and risks.

Across the game (hours): surface coziness → fossil-layer mystery → crystal boom and the start of sinking → living roots that fight your layout → the Heart, where the island's accumulated state decides which ending you can reach. Each stratum adds one new pressure and one new kind of value. The factory grows downward, and every level needs light carried to it.

4. The world

4.1 Grid and island

• Grid: 128 × 256 tiles, 8 × 8 px per tile. x runs 0–127 left to right and y runs 0–255 top to bottom.
• Surface line: y_s = 72. Rows 0–71 are open sky you can build into, up to 72 tiles of towers. Every tile you build adds mass (§6.7).
• Island depth D (rows of rock below the surface): seeded in [172, 184].
• Island surface width W0: seeded in [60, 76], centered at x = 64.
• Profile: half-width hw(d) at depth d rows below the surface, plus 1D value noise of ±2 tiles with a period of 12:
  • 0 ≤ d < 100: hw = W0/2 · (1 − 0.25 · (d/100)^1.5). This is the broad cup.
  • 100 ≤ d < 150: hw = W0/2 · (0.75 − 0.30 · (d−100)/50). Here the island narrows.
  • 150 ≤ d < D: hw = W0/2 · 0.45 · sqrt(1 − ((d−150)/(D−150))²). This is the root bulb that tapers to the tip.
  • Dangling root strands hang 3–14 tiles below the bulb as real root-wood tiles.
• Strata bands (d = rows below the surface): Surface/topsoil 0–11, Fossil 12–49, Crystal 50–99, Roots 100–149, Heart 150–D.
• Scaffolding: players may build out over the void within x ∈ [2, 125]. Built tiles need structural support (§6.7).
• World-gen stability guarantee: after generation, run the integrity solver. Any natural tile with integrity < 20 becomes stone. If that leaves an integrity < 20 tile, delete it. The starting island must have zero cracking tiles.

4.2 Time

• Simulation tick: 20 Hz (50 ms). All gameplay runs on ticks, and rendering interpolates.
• One Night = 24 real minutes = 28,800 ticks. There is no day. A Night has three Watches of 8 minutes each:
  • Dusk-watch (0–8 min): calm. Entities ×1.0. Rain chance at start: 20%.
  • Deep-watch (8–16 min): entities ×1.5, roots move (§8.4), and the Visitor may pass (§6.5). Rain chance: 25%.
  • Grey-watch (16–24 min): the calmest watch. Entities ×0.75. Rain chance: 45%.
• Moon: an 8-Night cycle. Phase index p = night mod 8 and moon light level by phase is [3,3,2,1,0,1,2,3] (p0 = full). See §6.4.
• Sleep: in a bed whose cell has warm light ≥ 8, the player can sleep until the next Dusk-watch. The sim keeps running at 8× speed with the screen dimmed, and any input wakes the player. Sleep clears 10 temporary warp, once per Night.

4.3 The starting island (all seeds)

A two-room plank house (3 tiles tall inside) with the Hearth, a bed, a table holding the first note, and a shelf. The Shed sits 10–14 tiles from the house with a broken alembic and a chest. There's a 6 × 2 garden plot, a pond of about 48 water cells (seeded 40–56), the Lantern Tree, two hanging lanterns (one lit), a ladder hatch through the floor, and Wick the cat. The shed's broken alembic leaks 0.4 flux/s until repaired. This is the first seed of dread, and it comes from the systems, not a script.

5. The player

• Body: collision box 6 × 14 px. Walk 5 tiles/s, jump 3 tiles high, coyote time 0.1 s, climb ladders and ropes at 3 tiles/s. No fall damage.
• Reach: place and break within 5 tiles. Hold-to-break times: soil 0.4 s, clay 0.8 s, shale 1.2 s, limestone 1.4 s, stone 1.6 s, root-wood 2.0 s, crystal 3.0 s (with a buoyancy preview and a hold-to-confirm), heartstone unbreakable.
• Inventory: 30 slots, stacks of 50, a 10-slot hotbar.
• No health, no hunger. The only player meter is Warp (§6.6).
• Falling off the island: the dark catches you. The screen fades and you wake at the hearth after a 3 s fade. You gain +5 temporary warp, and one random non-tool stack is taken to a midden (§6.5), where you can recover it.
• The Hearth sanctuary (hard rule): in any cell where the hearth's own warm light is ≥ 8, entities can't enter or spawn, dimmers can't attach to the hearth, and hallucinations never appear. The hearth burns 1 log every 6 min at full strength (warm 13). Unfed, it settles to embers (warm 6). It never goes fully out.

6. Systems

6.1 Essences and research

6.1.1 The essences

Everything is made of essences, measured in drams. They behave as fluids: they flow in pipes and are stored in jars.

Six primals. Their identities are fixed in every seed, and each has at least one surface source:

Taint is special: it can only be captured from flux (§6.3) and never synthesized. It counts as tier 1 when it appears as a parent.

24 compounds in 4 tiers. Every compound has exactly two distinct parents. At least one parent must be exactly one tier below it, and the other parent must be of a lower tier. Each compound has a recipe pool (its Correspondence) of four plausible parent pairs, and the world seed picks one per compound (§6.1.3). The pools keep the theme intact (Growth is never Ember + Hush), and the pick makes every seed a new puzzle. Pools deliberately overlap: Dew+Loam is a candidate for Growth, Salt and Ore, and Ember+Loam for Ore, Ash and Glass. So learning one recipe strikes candidates elsewhere, which makes the Ledger a cross-referenced logic puzzle. (i3: a 4th option was added to every pool; S05 shows 3 options made seeds too similar and puzzles too short.)

6.1.2 Items and their compositions

Item compositions are fixed across seeds, so players learn the world's materials. What changes per seed is what the compounds inside them are made of.

Synthesis only (found in no item): Mist, Vigil, Animus, Fetter, Dawn, Kindred. These are the compounds where deduction matters most, because the Separator (§6.1.4) can't be used on an essence you've never held.

6.1.3 Seeded recipe generation

1. Process compounds in tier order (T1 → T4), each in a seed-shuffled order.
2. For each compound, pick uniformly among pool options whose unordered pair isn't already used by another compound. If none is left, backtrack (it always succeeds; S05 ran 400 seeds).
3. Validation: every compound is synthesizable from primals plus Taint, and pairs are unique. Gate compounds (Glass, Metal, Animus) always resolve to surface primals; pools guarantee this.
4. Variety (S05, pool size 4):
   • 400 / 400 seeds produce distinct graphs.
   • Two random seeds share only 25% of their 24 recipes on average (pool size 3 gave 34%).
   • The rarest pool option still occurs in 16% of seeds.
   • Gate compounds' primal ancestry varies widely. For example, Metal needs Ember+Hush+Loam in 15% of seeds and Breath+Ember+Loam in 14%. So the early factory's essence chain differs per seed: one world wants dark Hush (nightshade, soot) for its pipes, another wants Breath (water, moonwheat).

6.1.4 Research actions

Every research action produces facts, and the Ledger (§15.4) records them automatically. Players deduce; the Ledger never deduces for them.

The Correspondence (D38). When a compound's glyph is first seen (in a distilled item, a blueprint's requirements, a clue, or an arranger's shelf), the Ledger shows its tier and its four candidate parent pairs. The puzzle is never "what could it be?" but always "which of these four is true in this world?". S05 showed that without visible pools the synthesis-only compounds cost 40–70 failed tests each: a grind, not a puzzle.

Research by the numbers (S05, 200 seeds, identifying all 24 compounds):

• Thinking saves half the failed tests. Exploration (clues) saves more, including half the permanent warp. Warp buys information, and deep scans cost permanent warp, which feeds the Become path. Guessing stays affordable for players who dislike puzzles.
• Where the difficulty lives: compounds you can hold are usually solved by 1–3 Prism scans. The six synthesis-only compounds (Mist, Vigil, Animus, Fetter, Dawn, Kindred) average about 1.4 failed tests each and are the boss puzzles: they must be reasoned out through the overlaps or found in journals.
• Deduction difficulty is stable across seeds (median 12, p90 16), so no seed is a dud.

Worked example (seed 7).

1. Glass's Correspondence is {Ember+Loam, Glim+Loam, Ember+Glim, Ember+Breath}. Ansel's note says "never from breath", so 3 candidates are left.
2. The player tests Ember+Loam and it fails: a violet puff that the hearth clears in about 30 s. Ember+Loam is now struck from Ore's and Ash's pools too.
3. Glim+Loam succeeds. Glass is identified, and Glim+Loam is struck from Growth's and Salt's pools.
4. Growth, held from a leaf, is left with {Dew+Loam, Dew+Glim, Hush+Loam}. One Prism scan shows Dew, a second shows Loam, so Dew+Loam is confirmed with no failed test.
5. That strikes Dew+Loam from Salt and Ore. Salt is left with {Dew+Ember, Dew+Glim}, and Ore with {Hush+Loam, Breath+Loam}. In this world Ore is Hush+Loam, so its Metal needs Hush, and the player starts planting nightshade.

Identifying compound X means its full recipe is confirmed by a successful Crucible test or a Separator. Identification unlocks synthesis of X and every blueprint gated by X (§11). Identifying a T3 or T4 compound adds +2 permanent warp: knowing it changes you.

First research chain (tutorial, every seed): the note on the hearth table reads: "The alembic's bulb is cracked. Glass wants the fire, the dirt or the glimmer, and I never once got it from the breath. — A." Glass's Correspondence appears in the Ledger with Ember+Breath already struck, leaving 3 candidates. The player distills a log, soil and a glowfruit with the Hand Mortar and runs 1–3 tests (1 failure on average). Each failure teaches flux: a 360-mote burst makes a visible violet puff that the lit hearth (4 AE) clears in about 30 s. Success identifies Glass, unlocks the Glass Bulb, and repairs the alembic. This is Milestone 1's research chain.

6.1.5 Synthesis

An automated Crucible (§6.2) turns 1 A + 1 B into 1 X every 4 s. Flux per dram made depends on tier: T1 9, T2 18, T3 36, T4 72 (×9 since i2, §6.3.5). Deep essences are dirty to make.

6.2 Automation and logistics

6.2.1 Chores that become machines

6.2.2 Logistics rules

• Fluids (essences and water) move through pipes. A connected network carries exactly one fluid type. The type locks when the first fluid enters and unlocks when the network is empty for 5 s. If a second type tries to enter at a junction, that junction blocks (violet pilot), stops both flows and leaks 1 flux/s until it's fixed.
• Pipe network model: each network is a logistics graph, not a pressure sim. Sources (machine outputs, tanks set to "provide") feed sinks (machine inputs, tanks set to "request") at up to 8 drams/s per network. The nearest sink in pipe distance is served first, with ties broken by lowest tile index. A segment holds 4 drams, which is cosmetic and used only for the flow animation. No pumps are needed, and direction doesn't matter.
• Items never travel in pipes. They move by golem, chute (free, downward only), or Bucket Lift (upward, 2 items/s, Ember 1 dram/min per 10 tiles of height).
• Power: heat machines burn Ember drams per cycle. Machines within 6 tiles of a Crystal Tap run on Resonance and need no Ember (§6.7.3). After the Bind ending, Heartpower runs every machine on the island.

6.2.3 Machine catalogue

Sizes are in tiles (W × H). "Light" is what the machine emits (§6.4). Flux is per cycle unless marked /s.

Lamps (all 1×1; the hearth is fixed). Suppression capacity C is in AE: how many running alembics' worth of flux the lamp can clear (§6.3.6).

Lamp oil is crafted at the workbench: Ember 2 + Salt 1 makes 2 oil. Candles: Ember 1 + Leaf 1 makes 3 candles.

6.2.4 Golems

Golems are uncanny little helpers. They turn their heads to watch you, and they stop at the edge of the dark and stand facing it.

• Chalk routes: with the chalk tool, place up to 6 waypoints. Each waypoint has an action: Take (filter, quantity), Give, Wait (seconds), or Tend lamps (refuel every lamp within 2 tiles from carried fuel).
• In darkness: a golem that reaches a cell below its light threshold stops and waits, facing the dark. After 60 s in darkness, an Arranger within 20 tiles may borrow it. The golem walks into the dark and comes back at the next Dusk-watch carrying a random item from a midden. It is never destroyed.

6.3 Flux

Simulated (i2). Every number in §6.3 comes from docs/sims/S01_flux.py (tuning against five written targets) and is exercised in the coupled probe S09_emergence.py. The reference implementation is docs/sims/fluxcore.py; the build must match it step for step (§20.5 test 3).

6.3.1 State and units

• Each cell holds an integer flux in millimotes (u32). Gameplay thresholds and all numbers in this document are in motes (1 mote = 1,000 units).
• What the value means depends on the cell: air flux for air, absorbed flux for solid absorbent tiles, and dissolved flux for water.
• All transfers are integer floors, subtracted from the source and added to the destination, so flux is conserved exactly apart from explicit sources and sinks: Σ cells + R + suppressed + sunk + captured = emitted.
• Why millimotes: S01 showed that with 1 unit = 1 mote, floor() freezes every cell under 10–50 motes, and a 1 mote/s source rounds to 0 per step.

6.3.2 The unit of pollution: the Alembic-Equivalent (AE)

1 AE = 3 motes/s, which is one Alembic running flat out (18 flux per item, one item per 6 s). Every emitter and every sink in the game is quoted in AE, so a player can reason "this lamp keeps 6 alembics clean". S01 tuned the absolute scale: at 1 AE = 0.33 motes/s, a dark workshop could never reach the gleaner threshold.

6.3.3 Thresholds and effects

6.3.4 Update (5 Hz, every 4 ticks; pass order is fixed)

Rates are per-mille (‰) of the cell's flux per step.

1. Emit: each emitter keeps a carry accumulator in thousandths of a unit, so sub-unit rates emit exactly over time.
2. Gravity (flux is heavy), g = 60‰: each air cell sends floor(f·60/1000) to the cell below if that cell is air or water. Water dissolves it. This is equivalent to a bottom-to-top scan on a snapshot.
3. Diffusion, pairwise, from one snapshot:
   • air–air 100‰ of the difference;
   • water–water 150‰;
   • absorbent solid–solid 1‰ (about 4 tiles per Night).
4. Absorption, 2‰: an air cell sends floor(f·2/1000) into each absorbent solid below, left and right of it, up to the solid's cap. Caps: soil/grass 300, clay 150, shale 100, limestone 80, stone 50, root-wood 400. Crystal has cap 0 (it taints instead, §6.7). Plank, brick and glass are non-absorbent. Seep, 5‰: a solid above 80% of its cap sends floor(f·5/1000) into each adjacent air cell. Saturated ground gives flux back.
5. Dissolution, 4‰: air next to water (above or beside it) dissolves into the water.
6. Wind, 30‰ × s: sky-exposed air (no solid anywhere above) shifts sideways in the wind direction, where s ∈ {0,1,2,3}. Flux blown off the grid edge goes to R.
7. Off-island loss, 100‰: air cells more than 2 tiles outside the island hull send flux to the reservoir R.
8. Light suppression (§6.3.6).
9. Sinks: silverleaf, roots, scrubbers, vents, tide drain.
10. Rain (during rain fronts):
    • Scrub, 6‰: each sky-exposed air cell sends flux down its column to the ground (3%/s). Roofs pass it to the drip line, the nearest absorbent or water ground cell.
    • Runoff, 4‰: each exposed absorbent ground cell sends flux one column toward its drain direction, the nearest drop to lower ground or off the island edge on either side. Tile slopes are terraces, so a pure neighbor comparison would strand flux on every flat run. A basin holds its flux, like a puddle.

6.3.5 Emission table (in AE; motes = AE × 3)

What S01 measured (dark, closed 6 × 4 shed on a soil floor, no lamp):

Soil under the shed is tinged by 3–6 min and sits at its seep threshold (240) by 30 min. The ground is a buffer: one machine's flux soaks into the floor, and the air only climbs once the soil saturates. Big machines overwhelm it at once.

6.3.6 Light suppression (the lamp budget)

Each lamp has a suppression capacity C in AE (lamp table, §6.2.3). That's C·3/5 motes per flux step.

• Proportional, light-weighted removal. Each step, every air or water cell where the lamp's light is L ≥ 1 wants to lose floor(f · 30‰ · L / level): 15%/s right at the lamp, falling linearly to nothing at the edge of its light. If the total wanted fits in the budget, every cell gets it. Otherwise every cell's share is scaled down to fit.

  • Why (S09): a lamp that simply erased all flux in its radius made factories perfectly clean until a sudden collapse, so lamp placement never mattered. With proportional removal, haze is graded, thicker in dim corners and at the edge of the light, and where a lamp hangs matters (S09 E5).

• Strain = wanted ÷ capacity, as a 10 s EMA.

  • Strain ≥ 0.8: the lamp flickers. It's working near capacity. This is a warning, not a failure.
  • Strain > 2 for 60 s: it gutters. A Wisp Lantern's wisp flees and the lantern is left empty. A flame lamp loses 2 radius until strain < 1 for 30 s. Crystal and Dawn lamps never gutter; they only flicker.

• Measured (S01 §3b, closed shed, lamp at ceiling centre, peak air in motes):

  Load (AE)	Lantern (1.5 AE)	Wisp Lantern (6 AE)	Crystal Lamp (12 AE)
  1	peak 3	peak 3	peak 2
  1.5	peak 3, flickers	peak 3	peak 3
  3	gutters in 1.5 min	peak 6	peak 6
  5–6	—	peak 11–14, flickers	peak 9–11
  7	—	wisp flees in 3.3 min	peak 13
  9	—	wisp flees in 1.8 min	peak 17
  13	—	—	peak 53, flickers, holds

  A lamp at capacity shows faint haze and flickers. An overloaded lamp fails within 1–4 min, depending on the overload.

6.3.7 The reservoir: vented flux comes back

Vented and off-island flux accumulates in R. At the start of each rain front, 60% of R is deposited evenly over the drip-line ground cell of every island column. R decays by 5% per Night. Venting moves pollution in time and space: it never deletes it.

6.3.8 What the sims proved about flux

6.4 Light and darkness

• Levels: two channels per cell, warm (0–15) and cool (0–15). Both are integers.
• Propagation: a breadth-first max-fill from each source. The level drops per tile entered by: air 1, glass 1, water 2, any solid 4. Background walls don't block light. The light map is recomputed incrementally in dirty regions, at most 10 Hz.
• Safety light Ls = max(warm, floor(cool · 0.6)). Warm light is the strong deterrent and cool light the strong flux suppressor. This is a core strategic split (decision K3).
• Moonlight: sky-exposed cells get cool light equal to the moon level by phase [3,3,2,1,0,1,2,3]. Full moon gives Ls 1. It's mostly cosmetic but helps a little on bright nights.
• Ward Stones set the entity pathing Ls to 6 within 5 tiles. They aren't light: golems, warp and flux ignore them.
• Real entities occlude light: each real void entity subtracts 2 from both channels in its own cells (min 0). Hallucinations don't. This is a deliberate tell (§6.6).
• Player in darkness: after 10 s with Ls < 2 at the player, temporary warp rises 0.1/s, the vignette closes and faint handwritten whisper fragments drift at the screen edge.
• Lamps go out because of: fuel running out; rain (unroofed open flames get a 20% chance per rain-minute); wind 3 (candles 10% per minute); guttering under flux strain; dimmers (§6.5); roots shoving the lamp's tile (§8.4); and tide submersion, which halves radius (§6.7.4).

6.5 Void entities (no combat)

They never touch the player. They take, rearrange, whisper and dim. Light works as walls for them: an entity's navigation grid is every cell where Ls < tolerance. They pathfind with a flow field from their target, recomputed when the light map changes.

6.5.1 Void Attention

V = (F_total + 90·Taint_stored)/3600 + R/7200 + 0.5·T_rows + W/10 + 2·N_hollowed (flux terms rescaled ×9 in i2 with the emission scale; stored Taint drams count at 90 motes each, so hoarding captured flux still draws attention)

• F_total is total flux on the island, in all cells.
• T_rows is how many rows the tide has risen (§6.7.4).
• W is player warp and N_hollowed the number of hollowed organisms.

Spawning is checked every 30 s. While the summed cost of active entities is below floor(V), one entity spawns, with its type weighted by the stratum spawn table. Hard cap: 12 active. [UNSIM: S07 must confirm first-hour V gives 0–1 gleaners and mid-game V gives 4–8 entities.]

Spawn cell rules (all must hold): Ls = 0. Air flux ≥ the type's threshold: gleaners 50 (tinged), arrangers, whisperers and dimmers 150 (fouled) (D28), or the cell is under the tide. The cell is outside the camera view plus a 4-tile margin. Entities fade in over 3 s, and nothing ever appears on screen.

6.5.2 The four kinds

The Visitor (post-1.0 layer, §19.1; 1.0 keeps only the A08 deep-shape atmosphere): in a Deep-watch with V ≥ 20, there's a 25% chance; it never happens two Nights in a row. It's telegraphed 60 s ahead: water ripples, hanging lamps sway, Wick hides, and the stars below the island dim one by one. During its 90 s passage a vast shape crosses the void below and blots out stars. Entities move 1.5× faster, unwarded lamps lose 2 radius, and items on the ground in sky-exposed cells with Ls = 0 are taken into the void. It never does anything else.

6.5.3 Fairness rules (hard)

1. No entity destroys tiles, machines or golems.
2. Every theft goes to a visible midden when one is within reach. The Keeper's Log records it ("Something carried 14 Clay toward the deep."), and the map marks the midden with "?".
3. Every arrangement leaves a chalk mark and can be restored for 1 Night.
4. Nothing spawns in view, and nothing happens inside the hearth sanctuary.
5. Every pressure can be predicted from the light, flux and tide overlays.

6.6 Warp

• Warp W = P + T, capped at 100. P (permanent) comes from knowledge. T (temporary) comes from exposure.

• Sources:

  Source	Amount
  Identify a T3 or T4 compound	+2 P
  Distill a wisp	+1 P
  Read a sealed journal page	+2 P (once each)
  Touch the Heart	+5 P (once per Night)
  Prism scan	+1 T
  Separator	+3 T
  Whisper	+1 T
  Darkness exposure	+0.1 T/s (after 10 s with Ls < 2)
  Eat mutated fruit	+2 T
  Fall into the void	+5 T

• Recovery: in the hearth's light (warm ≥ 10), −0.05 T/s (3 per minute). Sleep −10 T (once per Night). Silverleaf tea −5 T. Petting Wick −1 T (once per Night). P never goes down, except that it resets to 0 in the Mend endless mode.

• Gifts (warp is also power):

  • W ≥ 20, Sight I: flux haze shows at 2× density without the lens, and the Ledger shows Prism results for compounds you've already Prism-scanned in faint color on hover.
  • W ≥ 40, Sight II: hovering a world tile shows its item composition without distilling it.
  • W ≥ 60, Sight III: gleaners' intended paths draw as faint lines.
  • W ≥ 80, Heart-sense: a faint compass to the Heart, and a preview of tonight's root movements.

• Costs (hallucinations):

  • W ≥ 20: peripheral flickers, shapes at the screen edge that always vanish when you look.
  • W ≥ 40: Echoes, hallucinated entities, one per 3 min. They look identical to real ones.
  • W ≥ 60: Echoes act out fake thefts and fake arrangements. Fake UI warnings appear (a fake crack warning, a fake "lamp out" icon), one per 5 min.
  • W ≥ 80: false map features, such as a fake tunnel or a fake pipe link, and a second moon in the sky.
  • W = 100: you black out and wake at the hearth one Watch later, with T reset to 0.

• Telling real from false (a learnable skill). Hallucinations:

  1. don't occlude light (the lamp glow behind them doesn't darken);
  2. leave no wake in the flux overlay;
  3. don't appear in water reflections;
  4. are ignored by Wick the cat, who hisses and arches at real ones within 10 tiles;
  5. vanish while seen through the Clarity Lens (Mind + Glass; 10 s per use, costs 1 Glim);
  6. never appear in the Keeper's Log, which records only real events. The second moon has no reflection in the pond.

6.7 Buoyancy, tide and structure

6.7.1 Lift and mass

• Lift L = Σ (24 × charge) over crystal tiles + 30 per occupied Lift Bladder + 200 per fed Lodestone Keel.
• Mass M = Σ tile masses + machines (2.0 per footprint tile) + pipes (0.3) + golems (1.0)
  • full water cells (1.0; partial cells pro rata) + stored items (0.01 each).
• Tile masses: grass/soil 1.0, clay 1.2, shale 1.4, limestone 1.5, stone 1.6, bone 1.2, crystal 2.0, root-wood 1.1, plank 0.4, brick 1.5, glass 0.6, heartstone 0 (it's the anomaly).
• Crystal charge (0–1, starts at 1): drops 1%/min next to air flux ≥ 150 and 0.5%/min per Crystal Tap. It recovers 0.5%/min while cool light ≥ 4 and flux < 50. A crystal tile under 0.5 charge renders violet (tainted).

6.7.2 Altitude

• Equilibrium altitude A_eq = 1000 + H · ln( (L/M) / (L0/M0) ) fathoms, with H = 600. L0 and M0 are measured at world-gen, so every seed starts at exactly 1000.

• Actual altitude A relaxes toward A_eq with time constant τ = 10 real minutes: A += (A_eq − A) · (1 − e^(−dt/τ)).

• Preview: hovering a crystal with the pick shows "A_eq → value" before the 3 s hold-to-confirm.

• Shape of the cost (crystal removed and nothing else changed, [UNSIM: S03]):

  Crystal mined	A_eq	Tide rows
  25%	827	0
  40%	694	13
  50%	584	27 (Heart chamber drowned)
  60%	450	44
  75%	168	79 (Roots drowned)
  90%	−382	147

  The first quarter is nearly free. After that, every crystal costs more than the last.

• Counterweights: jettisoning spoil (1,000 stone tiles ≈ +94 fathoms at mid-game mass); Lift Bladders (+30 each, so 20 wisps ≈ +35 fathoms, which is slow and clean); Crystal Nurseries (+1 crystal per 2 Nights, the Mend path); Lodestone Keels (+200 each while fed with Taint, the Bind path: you float on captured flux, so the factory must keep running).

6.7.3 Crystal Taps and Resonance

A Tap lets you use a crystal without mining it. It gives Glim 1 dram/10 s and Resonance power within 6 tiles (those machines need no Ember). The crystal's charge drains 0.5%/min, so a fresh crystal hits the 0.5 tainted threshold in 100 min and zero in 200 min. An untapped, clean, cool-lit crystal recovers. Rotating taps across crystals is sustainable and is a chore golems can take over. Mining a crystal instead gives 8 shards at once (Glim 24, Lift 16, Breath 8) and loses its 24 lift permanently.

6.7.4 The tide (the dark rising)

• T_rows = clamp((800 − A) / 8, 0, ∞). The tide line sits T_rows above the island's lowest tile.
• Cells under the tide: light sources there have half radius (floor). Entity spawning needs only Ls = 0, with no flux requirement. Flux drains into the void at 2%/s, which raises V through the T_rows term. Visually, a slow indigo fog covers them.
• Foundering: at A ≤ −700 the tide covers the island. The run ends as Foundered (§9.4). It's telegraphed for hours by the depth ruler, the tide line, and the Keeper's Log.

6.7.5 Structure and integrity

• Integrity (0–100) is computed per solid tile as a max-propagation from anchors: crystal (40 + 60 × charge), root-wood (70), heartstone (100), and placed support beams (100 when standing on a supported tile).

• Propagation: a tile's integrity is the max over its neighbors of neighbor − cost. The cost depends on direction and material, and a tile can't go above its material's maximum:

  Material	Max	Resting on (support from below)	Horizontal	Hanging (support from above)
  Soil / grass	60	0	12	20
  Clay	70	0	10	15
  Shale	50	0	16	25
  Limestone	80	0	8	12
  Stone	100	0	6	10
  Root-wood	70	0	4	2
  Plank	50	0	8	10
  Brick	90	0	6	10
  Support beam	100	0	2	2

  This gives an unsupported span of about 10 tiles in soil, 6 in shale and 32 in stone.

• Integrity ≤ 0: the tile cracks. You get 30 s of visible cracks and falling dust, then it falls as rubble. Rubble drops straight down and settles as a loose rubble tile on the first solid below, or leaves the island (removing its mass).

• Detached region (no path to any anchor): the whole chunk shakes for 5 s, a log entry appears, then it falls as one piece. Everything on it is lost to the void, including machines. This is the harshest consequence in the game, and it's always preceded by visible cracks unless the player cut the last connection themselves.

• Auger vibration: tiles within 2 tiles of a working Auger lose 5 integrity, which can crack shale.

• Integrity is recomputed incrementally within 32 tiles of any change.

6.7.6 Tilt

• θ = clamp(30° · (x_M − x_L) / W0, −15°, +15°), where x_M is the center of mass and x_L the center of lift.
• |θ| ≥ 2°: lanterns sway, and water and air flux drift toward the low side (floor(f · |θ|/100) per step).
• |θ| ≥ 5°: the pond spills over its low rim and the water is lost, rubble slides one tile per 2 s, and golems move 20% slower uphill.
• |θ| ≥ 10°: unanchored furniture and chests slide, loose items fall off the low edge, and you can't sleep.
• Rendering: the island stays grid-aligned and the sky rotates (ART_BIBLE §4.6).

6.8 Water and weather

• Water is a cellular fluid with 0–8 levels per cell at 10 Hz. It falls if it can, then equalizes sideways. Water that leaves the hull falls into the void and is lost. It carries dissolved flux in proportion. Pond intakes (Metal 2) put up to 8 water drams/s into a pipe. Rain barrels (plank 4) collect 1 dram per 10 s per rain intensity, up to 64.

• Weather states: Clear, Overcast, Rain (intensity 1–3), plus Mist and Gale as a post-1.0 layer (§19.1). Until then, transitions into Mist or Gale become Overcast. Transitions happen at Watch boundaries:

  From \ To	Clear	Overcast	Rain	Mist	Gale
  Clear	0.50	0.30	0.10	0.10	0.00
  Overcast	0.20	0.30	0.35*	0.10	0.05
  Rain	0.10	0.40	0.40	0.05	0.05
  Mist	0.35	0.30	0.15	0.20	0.00
  Gale	0.10	0.40	0.40	0.00	0.10

  *During the Grey-watch the Overcast → Rain chance is 0.50, taken from Overcast → Overcast. The Watch rain chances quoted in §4.2 are approximate summaries of this table.

• Rain: adds water to the top cells of sky-exposed columns (intensity 2 adds 1 level per column per 30 s). It scrubs air flux down to the ground (§6.3.3 step 10), deposits the reservoir (§6.3.6), and puts out unroofed flames.

• Wind: direction ±1 and strength 0–3, re-rolled at each weather change. Gale is always strength 3. Wind moves surface flux, clouds and rain angles, and it can put out candles.

• Mist: cool light radius −1 on the surface, and wisps spawn 2× as often.

6.9 Flora and fauna

Mutation rule: each organism tracks exposure, meaning soil flux at its root cell (plants) or air flux at its body (fauna). Normal → Turned after 4 cumulative minutes at ≥ 150. Turned → Hollowed after 4 more minutes at ≥ 400. Turned organisms give their mutated products, some of them rare (Hollow bark is the earliest source of Echo). Hollowed organisms emit 0.5 flux/s and count in V. Mutation is reversible from Turned (2 Nights at < 50) but not from Hollowed. Cultivating a deliberate "flux garden" is a valid strategy.

6.9.1 Wisps

• They spawn at pond surface cells while the pond's average dissolved flux is < 50 and the pond has ≥ 8 water cells. Rate: 1 per 3 min (1 per 1.5 min in Mist). Cap: 1 per 8 pond cells, max 6.
• They drift within 6 tiles of the pond, flee air flux ≥ 150 (despawn), and like cool light.
• Catching one with the net takes a 1 s hold. Bottled wisps sleep inside Wisp Lanterns and Lift Bladders. A released wisp flies back to the pond.
• Wisp roads: a continuous chain of cells with cool ≥ 4 and flux < 50 from the pond to another body of water of ≥ 8 cells lets wisps migrate and spawn there too. This is how wisps reach the deep, and the Mend ending needs it (§9.1).

6.9.2 Wick

Wick wanders between the hearth and the player inside lit cells only (Ls ≥ 3), and sleeps by the hearth during the Deep-watch. Wick hisses and arches at real entities within 10 tiles and ignores hallucinations. At W ≥ 80, Wick won't leave the hearth. Petting gives −1 T warp once per Night. Wick can't be harmed, taken or mutated. Wick is the game's promise that some warmth is unconditional.

7. System interaction matrix

Read across: how the row system affects the column system.

Feedback loops and what the sims showed (S09, docs/sims/S09_emergence.results.md; a 64 × 72 island slice running flux, lamps, the pond and wisps, weather, crops, crystal charge, vents and scrubbers together; nothing scripted):

1. Factory runaway: proven, with a tipping point and hysteresis. Two Wisp Lanterns (12 AE) uphill of the garden hold through 12 AE. At 13 AE they collapse after 43 min. At 14+ AE they collapse in 2–3 min, flux rolls down the slope, the pond fouls in 9–12 min, crops turn, and V jumps from 1.8 to 28–37. Path dependence: a base that ran one Night at 16 AE and was then torn back to 8 AE stays collapsed (pond 1,569 motes, lanterns empty, 4 crops turned), while the same base at 8 AE throughout stays clean. The saturated ground keeps seeping, and re-lit lanterns flee again. Design consequence: a gradual expansion is safe, a sudden one can lock the base in a fouled state, and recovery needs scrubbing or time, not just switching machines off.
2. Rain return: proven. With a vent, the workshop stays spotless, but garden soil jumps at exactly minutes 24, 48 and 64, which are the three rain-front starts. The pond fouls at the first front and 2 crops turn by Night 3. Doing nothing fouls the pond more slowly (42 min, via the door and runoff). A scrubber keeps everything clean, which revealed a dominant strategy that i2 fixed (scrubber nerf plus stored Taint counts toward V, §6.2.3, §6.5.1).
3. Sinking spiral: partly proven. An over-built factory in the crystal cavern taints the crystal around it: A_eq drops 44 fathoms in 3 Nights without mining a single crystal. The tide feedback awaits S03.
4. Clean-pond loop: proven as the stable branch of loop 1. Below capacity, lanterns keep the pond clean, the pond keeps spawning wisps (6 at the end of every stable run), and the player can always refill. A chronic leak still matters: even a healthy 8-AE workshop uphill tinged the pond (66 motes) over 3 Nights.
5. Root regulation: not yet modelled. Pending S09-roots (Roots stratum).

Layout decides what fails (S09 E3). The same over-built factory (8 AE on a 6-AE lantern) fails differently by site:

The same machine count hits the wisps, the entities, or the island's buoyancy depending only on where it was built. That's the "factory layout shapes where corruption collects" promise, measured.

Survey (S09 E4). 24 random bases built near their limits gave 11 stable, 7 pond-first and 6 lamp-first failures, at times from 1 to 68 min. Lamp placement (E5): the same two lanterns let between 112 and 277 motes leak out of the door depending on where they hang.

8. Strata

8.1 Surface (d 0–11) — "The Hearth"

• What's there: the house, hearth, shed, garden, pond, Lantern Tree, Wick, moths, frogs, nightshade, and topsoil with clay pockets. Moonlight and weather apply.
• New mechanics: the first research chain (Glass), the Alembic, lamps and fuel, wisps, flux leaking and sinking into soil, gleaners, rain.
• Pacing: 0:00–1:30. Signature moment: lighting the shed so the thing in the dark can't come back in.
• Ends when the first shaft breaks into the fossil layer and you find the first skeleton's hand still holding a lantern.

8.2 Fossil layer (d 12–49) — "The Ossuary"

• What's there: shale (brittle) and limestone, bone inclusions, fossil ferns and bone moss. 3–4 keeper sites: a skeleton, a journal (8 pages), a tool cache (old iron, a bone pick), and a broken machine you can repair. Natural pockets of air are pitch dark, with no moonlight.
• New mechanics: structure (shale spans are short, so beams matter), golems (Animus is the second big puzzle), journals and clues, the Separator, arrangers and whisperers, middens, Hush and Bone essences.
• Pacing: 1:30–4:00. Signature: following a dead keeper's chalk route to their last room.

8.3 Crystal layer (d 50–99) — "The Keel"

• What's there: stone with crystal veins and geodes, 380–460 crystal tiles concentrated toward the center. Glass lichen glows on charged crystal, so this layer has its own cool ambient light where crystal is exposed.
• New mechanics: buoyancy and the depth ruler, taps and Resonance, crystal lamps, augers for bulk digging, lift bladders, spoil jettison, tilt, dimmers, and the Visitor.
• Pacing: 4:00–9:00, the factory boom. Signature: watching the equilibrium needle dip as you hold the pick on your first crystal.

8.4 The Roots (d 100–149) — "The Underlung"

• What's there: root-wood tiles (living, anchors, flux sinks at 0.3 AE per tile in contact), root-blooms, and middens tend to form here.
• Root behavior: during each Deep-watch, every root tip (a root tile with exactly one root neighbor) takes up to 3 growth steps, one every 2.5 min. Each step picks the neighboring cell with the best score: +flux/100 − Ls·2, where a non-root solid scores −5. A step into a cell holding a pipe or a 1×1 machine shoves it one tile along the growth direction. If it can't move, it disconnects and leaks 1 flux/s at the joint. A step into air or soil converts that cell to root-wood. Roots never enter cells with Ls ≥ 6 or within 2 tiles of a Root Stake.
• New mechanics: living terrain, root management (stakes, and feeding them flux on purpose), and the Root, Dream and Echo essences.
• Pacing: 9:00–13:00. Signature: coming down after the Deep-watch and finding your pipe run bent into a curve that points at the Heart.

8.5 The Heart (d 150–D) — "The Seed"

• What's there: the Heart chamber, a 22 × 12 pre-carved cavity with a heartstone floor. The Heart sits in the middle: 8 × 8 tiles, an enormous seed that is half crystal, half root. It pulses with an inverse light: a ring of darkness at −3 levels within 6 tiles that breathes on a 12 s cycle. All three ending archetypes have left remains here: a Gardener's dried pool with empty wisp jars, an Engineer's four broken Fetter Pylons, and a Scholar's skeleton curled against the Heart.
• New mechanics: the ending accumulators (§9), heartstone dust (Abyss), and touching the Heart (+5 P).
• Pacing: 13:00–18:00. Signature: the chamber reading your island back to you.

9. Endings (earned through play)

When the player first touches the Heart, its three accumulators become visible through Heart-sense (W ≥ 80) or the Heart's Stethoscope (Mind + Metal), as three slow pulse rhythms. Each accumulator fills only while the world is in a specific sustained state. There is never a menu, a prompt or a dialogue choice. The states exclude each other: Mend needs the chamber lit and clean, Bind fills it with pylon flux, and Become needs it dark.

9.1 Mend — "Dawn"

• Accumulates +1 per minute while all of these hold:
  1. every Heart-chamber cell has Ls ≥ 6 (Dawn Lamps are the practical way to get there);
  2. maximum air flux in the chamber is < 50;
  3. island total flux F_total < 15,000 motes;
  4. a continuous chain of cells with Ls ≥ 3 runs from the hearth to the chamber (the lantern path);
  5. at least 6 wisps live in the chamber, which needs a Kindred Pool (a ≥ 8-cell water body treated with Kindred 10) and a wisp road down to it.
• Decays −2 per minute when any condition fails. Completes at 180.
• Result: dawn breaks. The sky blends into the dawn range of the palette, the island becomes a living world, and the void entities retreat to the deepest dark.
• Endless mode (Day): sky-exposed cells count as Ls 8. Entities exist only below d = 50. P warp resets to 0. New goals: re-grow crystal and turn tainted ground into gardens.

9.2 Bind — "Unending Night"

• Accumulates +1 per minute while 8 Fetter Pylons surround the Heart (each within 10 tiles of it), and each one is fed Taint ≥ 0.5 dram/min and Ember ≥ 1.25 dram/min (about 4 Taint and 10 Ember per minute in total). Decays −1 per minute per starved pylon. Completes at 240.
• Result: the Heart is harnessed. Heartpower runs every machine on the island without Ember. Night stays.
• Endless mode (Engine): the pylons must be fed forever. If they're starved for 10 minutes, the binding slips (−1 per minute) and V grows by +5 per Night. The factory must grow.

9.3 Become — "The New Heart"

• Triggers when W ≥ 90 with P ≥ 60, and the player stands still for 3 continuous minutes within 2 tiles of the Heart while every chamber cell has Ls = 0. To get there you have to put out every lamp in the chamber yourself.
• Result: the player lies down. The screen holds on the dark, and the cat's silhouette waits at the top of the shaft.
• Endless mode (Succession): a new keeper wakes at the hearth on the same island, a century later. Lamps are out, pipes are cracked (each pipe segment has a 50% chance to be broken), golems are fossilized and repairable, and the player's own skeleton lies at the Heart. The Ledger keeps what you learned, and the essence recipes stay the same. The old keeper's auto-journal (§13.4) is scattered as journal pages.

9.4 Foundered (failure, not an ending choice)

At A ≤ −700, the night takes the island. A Keeper Record is saved: name, Nights survived, the auto-journal, and the layout of one chosen room. It can appear as a fossil-layer keeper site in future new worlds (§12).

9.5 Why it lands

The three keepers you've been reading about all made one of these choices, and their remains are in the chamber. By the time you arrive, your island already leans one way: low flux and wisps (you were careful), a deep Taint economy (you built the engine), or high warp (you wanted to know). The ending you reach is the one you've been living, and then you get to keep living it.

10. Key decisions

11. Progression and unlocks

Hour targets [UNSIM: S06 pacing sim]: Glass by 0:20, Alembic running by 0:25, Metal and pipes by 1:15, Animus and golems by 2:30, first crystal by 4:30, Roots by 9:00, Heart by 13:00, first ending 15–20 h.

12. Replayability and seeds

What differs across seeds, and why it matters:

1. The essence recipe graph (§6.1.3). S05: every seed's graph is distinct, two seeds share only 25% of recipes, and the gate compounds' primal needs vary. Each run's research is a fresh deduction puzzle, and your factory's production chains differ. If Vigil is Spark+Glim, wards come early; if it's Spark+Shade, it needs Hush, and wards wait for the dark.
2. Island shape: W0, depth, profile noise, crystal distribution (veins vs geodes, centered vs lopsided, which affects tilt), fossil pockets, root seeds, pond size.
3. Keeper sites: which lesson keepers appear (2 of the Digger, Wanderer and Miner) and where, plus seeded clue content and which keepers' clues are false.
4. Weather bias: wind prevailing direction and rain frequency (±30%).
5. Charters (optional modifiers chosen at world creation, inspired by Against the Storm): Heavy Keel (−25% crystal), Old Pond (pond ×2, wisp cap 10), Restless Roots (root steps ×2), Thin Night (V ×1.25, more clues from whisperers), Lost Ledger (no first note; Correspondences stay hidden until a journal page reveals each one, the hard mode S05 shows costs 10–20× more failed tests), Inheritance (start with a Keeper Record site).
6. Endings: three structurally different builds (clean wisp roads, a Taint engine, or a warp descent).
7. Keeper Records: foundered or Become runs leave the player's own keeper in future worlds.

13. Narrative delivery

No cutscenes. The story is told through:

13.1 Keepers (6 total; the Heart chamber always shows the three ending archetypes)

Each seed places Ansel, Tamsin and Ilse plus 2 of Odo, Bram and Merrit.

13.2 Environmental storytelling

Skeleton poses, a dead keeper's chalk routes still on the walls, the broken machines, tide-line scratches, and distant islands whose window lights go out one by one over the Nights (pure storytelling; one goes dark every 3 Nights).

13.3 Clue templates (seeded content)

• "Where {A} lies down with {B}, {X} wakes." → A+B = X (true or false by keeper).
• "{X} remembers {A}." → A is a parent of X.
• "I never got {X} from {A}. Not once." → A is not a parent of X.

13.4 The Keeper's Log (auto-journal)

The game writes short handwritten lines when real events happen: first wisp, first theft, first crack, tide milestones, and so on. It's diegetic feedback and one of the tells (hallucinations are never logged), and it becomes the next keeper's journal.

14. The first hour (systemic, not scripted)

Hook: you have a machine, a mystery, and proof that your choices shape where the dark comes from. [UNSIM: S06 must show this hour's chores and timings are reachable; playtest at M1.]

15. UI/UX and legibility

15.1 HUD (diegetic where possible)

• Hotbar at the bottom: 10 slots, 16 × 16 each.
• Depth ruler on the right edge: a brass gauge showing altitude A, a ghost needle for A_eq, the tide line, and the Founder mark.
• Warp sigil at the top left: an eye that opens in 5 stages, with the P part drawn as a solid iris ring.
• Watch and moon at the top right: the moon phase icon plus a 3-segment watch arc.
• Keeper's Log at the bottom left: three lines of fading handwriting.

15.2 Lenses (hold a key or toggle; all palette-locked overlays)

• Flux lens (F): a heat map in the R4 ramp with contour lines at 50/150/400/800, plus arrows for the net flux direction per 4 × 4 tile block.
• Light lens (L): warm/cool areas outlined, Ls shown as stepped contours, and dark paths: dotted lines along the routes entities could take to each container (they turn red-violet when a path exists).
• Structure lens (S): integrity as stone ramp shades, with cracking tiles blinking.
• Buoyancy lens (B): crystal tiles colored by charge, the tide line, and a preview of the center-of-mass vs center-of-lift.
• Map (M): 1 pixel per tile for the whole island, with any lens overlaid; middens "?", chalk spirals, lamp status.

15.3 Without lenses

Flux shows as haze density, light as the light itself, strain as flicker, integrity as cracks, altitude as the ruler and the sky. The reservoir R shows in the clouds: cloud layers swap R1 shades for R4 shades in proportion to R (one cloud band per 2,000 motes, up to all of them), so the player watches vented flux gather overhead before it rains. When a front deposits, the Keeper's Log writes "The rain tasted of the vent." Every important state has a non-lens signal.

15.4 The Ledger (research UI)

A book with one page per essence, plus a spread-out Correspondence board.

• Essence page: glyph, tier ring, which items contain it, Prism colour bands revealed so far, and its four candidate pairs. Each candidate shows the facts that touch it:
  • ✗ when that pair was tested and makes nothing;
  • "✓ is Glass" when that pair is confirmed as another compound's recipe;
  • a dimmed swatch when a revealed Prism colour rules it out.
• Player marks: the player crosses out, circles or stars candidates. The Ledger records facts and displays them where they apply, but it never draws a conclusion: it won't strike a candidate just because the facts imply it.
• Correspondence board: all seen compounds as a grid of their candidate pairs, with shared pairs linked by thin ink lines. This is where the overlaps that make the puzzle become visible (Dew+Loam links Growth, Salt and Ore).
• Pair grid (M5, cuttable): a 7 × 7 (primals plus Taint) and, later, a compounds grid of every pair ever tested.

15.5 Machine status (pilot lights; shape and color both encode state)

Steady amber: working. Blinking amber at 1 Hz: starved of input. Steady cyan: output full or blocked. Blinking violet: flux-strained or error. Dark: off.

15.6 Visual-first feedback (hard rule)

No information is ever carried by sound alone. Every warning, tell and telegraph in this document has a visual form: lamp stutter, dust, shaking, handwriting, Wick's pose, the Log. That makes the audio deferral (§16) safe, and it's also an accessibility guarantee.

15.7 Accessibility

Every color code is doubled with shape or blink. Hallucinations can be turned off in options (the game then logs "Echo (hidden)" instead), and turning them off disables the Become ending's Sight bonuses. No flashes faster than 3 Hz. Screen shake is at most 1 px.

16. Audio direction (brief) — DEFERRED

Owner decision (after i1): skip audio for now. Audio is out of scope for M0–M5, no milestone or acceptance test depends on it, and the design loop doesn't spend iterations on it. The game must be fully playable and readable silent (§15.6). The notes below are kept only as future direction. The build should leave a no-op audio event hook (sim events like lamp_strain, crack, whisper and visitor_telegraph already exist for the Log), so sound can be added later without touching the sim.

• Cozy bed: music box and harmonium motifs, the hearth crackle, rain on the roof, the pond's frogs. Near the hearth the mix is warm and close.
• Machines: soft clockwork, glass bubbling and gentle hisses, tuned to one key (D minor pentatonic) so a factory hums in tune.
• Dread layer: a low drone whose volume follows local flux and whose detune follows warp. Whispers are panned toward their source. Structural creaks are directional. The Visitor is a sub-bass swell with no attack.
• Rules: no stingers or sudden loud sounds; every new sound fades in over at least 300 ms. Under the tide, a low-pass filter makes everything muffled.
• Production: procedural and synthesized sources (oscillators, filtered noise, granular rain), recorded in-house or CC0 only, with each CC0 file justified in DECISIONS.md.

17. Tuning parameters (starting values)

All values are hand-derived for iteration 1. Sim column names the simulation that must confirm them.

Planned simulations: S01 flux spread and pooling · S02 lamp budget vs factory size · S03 buoyancy curves and counterweights · S04 structural stability of generated islands · S05 research solver (experiments needed, seed variance, value of clues) · S06 economy and pacing · S07 attention and spawns · S08 water, rain and reservoir · S09 coupled emergence probe.

18. Risks and mitigations

19. Scope

Measured (i4). docs/sims/S10_scope.py counts the real asset list and sizes the build with an assumption-labelled effort model. Re-run it whenever ART_BIBLE §10.2 changes.

19.1 Core, layers, and cuts (decided i4)

Core: 1.0 ships these

• Essences: 6 primals, Taint, 24 compounds with seeded Correspondences. These are data, so cheap per compound.
• Research: Ledger, Crucible tests, partial Prism, Separator, journal clues, arranger shelves, whisperer statements.
• Machines (21): Alembic, Crucible, Pipe/Valve, Jar/Cistern, Chest, Chute, Bucket Lift, Golem Workshop, Auger, Spoil Chute, Vent, Scrubber, Ward Stone, Crystal Tap, Assembler, Separator, Lift Bladder, Crystal Nursery, Lodestone Keel, Root Stake, Fetter Pylon.
• Lamps (6): Candle, Lantern, Ember Lamp, Wisp Lantern, Crystal Lamp, Dawn Lamp. Plus the hearth.
• Golems (3): Clay, Bone, Glass.
• Entities (4): Gleaner, Arranger, Whisperer, Dimmer.
• Systems: flux (all passes), two-channel light, warp with all 6 hallucination tells, buoyancy, tide, crystal charge, structure and integrity, tilt (sway plus pond spill at 5° only), cellular water, weather (Clear, Overcast, Rain, with wind), mutation, wisps and wisp roads, roots.
• World: 5 strata, 6 keepers' content, Wick.
• Endings: 3 + Foundered, each with an endless mode.

Layers: post-1.0, designed but not built

• Charters (the Lost Ledger toggle ships as an option because it's trivial).
• Keeper Records across worlds.
• The Visitor as a gameplay event (the deep-shape parallax stays as atmosphere).
• The Root golem.
• Mist and Gale weather.
• Tilt sliding (only sway and spill ship).
• The research pair grid.
• Gamepad.
• Tauri desktop build.
• Audio (deferred by the owner, D25).

Cut from the design outright: the Lure, the Root Graft and the Glowfruit Lamp. Each one duplicates a role a core item already covers: decoys duplicate light placement, grafts duplicate stakes plus flux feeding, and the glowfruit lamp duplicates the candle.

19.2 Milestone sizes (S10)

A focused 2D tile sim with cellular fluids, lighting, UI and tests usually lands at 25–45 kLOC, so the estimate is within range. M0 + M1 is 46% of the code because it builds every foundation (renderer, sim core, UI kit). Each later milestone is mostly content and rules on top of it.

19.3 The M1 manifest (the smallest slice that proves the promise)

World. The surface island only: the GDD §4.3 starting layout on a 64-wide island with 12 rows of soil and clay over undiggable bedrock (B07a). There are no lower strata and no buoyancy.

In M1, with simplifications:

Not in M1: strata below topsoil, structure, buoyancy, pipes, golems, warp and hallucinations, arrangers, whisperers, dimmers, wind, runoff, the reservoir, mutation, the Prism, the map view.

M1 is a slice for the 10-minute acceptance test, not the whole first hour: §14's 0:50–0:58 beats (the tool cache, the fossil hand) need the fossil layer, so the full first hour becomes playable at M2.

19.4 M1 internal checkpoints (each one deployed when green)

1. M1.1 "Night island":
   • renderer with the palette LUT; sky, moon, clouds, rain and parallax;
   • procedural tiles; the player walking, digging and placing;
   • static lamps lighting the scene;
   • lanternforge check passing on all assets.
2. M1.2 "The leak":
   • flux core passes with haze and the lenses;
   • lamps with fuel, strain and gutter; the hearth;
   • the pond and rain; wisps, net and lantern; Wick; the Keeper's Log; Nights and Watches.
3. M1.3 "The first machine":
   • Ledger and Glass chain; Alembic repair and automation;
   • gleaners and middens; the weather Markov;
   • all M1 acceptance tests (§20.4).

19.5 AI art is an owner step (D41)

The build agent may have no image model, so AI generation is never a blocking build step.

• Prompts: the build ships assets/prompts/<id>.txt for every C-asset, from the ART_BIBLE §10.4 template.
• Drop folder: the owner drops generated PNGs into assets/ai_raw/<id>.png, and lanternforge clean turns them into game sprites.
• Placeholders: until a C-asset arrives, the build uses a code-drawn placeholder from a small shape spec (assets/placeholders/<id>.json: rects, ellipses and lines in palette indices, outlined by the same rule). These are marked in the debug overlay.
• Pipeline proof: lanternforge is proven end to end on a synthetic "AI-like" input, a high-resolution, anti-aliased, off-palette rendering of the Alembic generated by code. M1 acceptance 4 is then re-run when the real AI Alembic lands.

20. Build handoff

20.1 Recommended stack

• TypeScript (strict), Vite, WebGL2. A thin custom renderer, with twgl.js allowed as a helper. It runs in the browser and can be packaged later with Tauri.
• Why: an agent can build and test it headlessly (Vitest for the sim, Playwright for screenshots); the custom palette-index renderer (ART_BIBLE §3) fits raw WebGL2 better than a scene-graph engine; the 32k-cell grid is cheap in JS with typed arrays.
• Art tools: Python 3.11+ with Pillow and NumPy (tools/lanternforge), tested with pytest.

20.2 Architecture

/src
  /sim        pure, deterministic, no DOM, no floats in persisted state
    world.ts (grid, typed arrays per field), rng.ts (sfc32 streams per system)
    tiles.ts, flux.ts, light.ts, water.ts, structure.ts, buoyancy.ts, weather.ts,
    time.ts, entities.ts, warp.ts, research.ts, machines.ts, golems.ts, logistics.ts,
    roots.ts, endings.ts, log.ts, commands.ts (player input as serializable commands)
  /render     reads sim state read-only after each tick; never mutates it
    renderer.ts (index buffer → light resolve pass), sky.ts, particles.ts, parallax.ts,
    lut.ts, overlays.ts
  /ui         ledger, HUD, lenses, menus (renders into the same index buffer, unlit)
  /data       JSON definitions (schemas §20.3), validated at load with zod
  /app        main loop: fixed 20 Hz sim, rendering at display rate with interpolation
/tools/lanternforge   Python art pipeline (ART_BIBLE §10)
/tests        vitest (sim), playwright (render), pytest (tools)

• Determinism: the sim uses integers only. Fixed-point is 1/1000 where fractions are needed, and altitude is an integer in millifathoms. ln() uses a fixed table with 4096 entries and linear interpolation in integers. There's no Math.random, and no iteration over Map or Set where order matters. Each subsystem gets its own seeded RNG stream: worldgen, flux, weather, entities, research, roots, warp.
• Commands: all player actions become Command objects stamped with a tick. Replay = seed + command log. Saves are a JSON header plus RLE-compressed typed arrays.
• Update order per tick: commands → player → machines/logistics → golems → entities (5 Hz) → flux (5 Hz) → water (10 Hz) → light (dirty, ≤ 10 Hz) → structure (on change) → buoyancy (1 Hz) → weather/time → roots (Deep-watch) → endings (1 Hz) → log.
• Performance budgets (mid laptop): sim tick average ≤ 4 ms; flux step ≤ 3 ms; light recompute ≤ 2 ms per dirty region; render ≤ 6 ms.

20.3 Canonical data and schemas

The data already exists. docs/data/*.json holds:

• 31 essences with their pools, 35 items, 19 recipes, 19 tiles;
• 31 machines, 7 lamps, 3 golems, 11 tools, 4 entities;
• 5 strata, 7 LUT zones, and every tuning parameter.

It's generated by docs/data/make_data.py and checked by docs/data/validate.py (i5: 176 records, 0 problems). The validator checks referential integrity, the pool tier rules, the synthesis-only set, that every essence has a use, that the flux params match S01, and that the S05 recipe generator succeeds on 500 seeds. The build copies these files verbatim to /data and validates them at load with zod schemas mirroring the interfaces below. When a number changes, change make_data.py, re-run it, then update the GDD text.

type Id = string;
type Ref = `item:${Id}` | `essence:${Id}` | `place:${Id}` | `tool:${Id}`;
interface Essence { id: Id; name: string; tier: 0|1|2|3|4; color: number /*palette idx*/; glyph: Id;
  pool: [Id, Id][] | null /*4 pairs; null for primals and taint*/; synthesisOnly: boolean;
  captureOnly?: boolean /*taint*/; identifyWarpP: number; }
interface Item { id: Id; name: string; stack: number; mass: number; composition: Record<Id, number>;
  sources: string[]; icon: Id; fuel_s?: number; distill_warp_p?: number; per_tile?: number; [k: string]: unknown; }
interface Recipe { id: Id; station: "hand"|"workbench"|"assembler"; inputs: {ref: Ref; qty: number}[];
  outputs: {ref: Ref; qty: number}[]; unlock: Id[]; timeS: number; }
interface Tile { id: Id; solid: boolean; mass: number; digS: number /*-1 = unbreakable*/; fluxCap: number;
  absorbent: boolean; lightCost: number; drops: {item: Id; qty: number}[]; strata: string[]; procgen: Id;
  integrity?: {max: number; rest: number; horiz: number; hang: number; anchor: string | null}; }
interface Machine { id: Id; size: [number, number]; unlock: Id[]; build: {ref: Ref; qty: number}[];
  behavior: Id /*key into the behavior registry*/; params: Record<string, unknown>; }
interface Lamp { id: Id; unlock: Id[]; channel: "warm"|"cool"|"both"; level: number; fuel: Ref;
  fuelSecondsPerUnit: number | null; suppressionAE: number; [k: string]: unknown; }
interface Golem { id: Id; unlock: Id[]; recipe: {ref: Ref; qty: number}[]; speedTps: number; carryItems: number;
  carryDrams: number; minLs: number; fluxAE: number; climbs?: boolean; light?: [string, number]; }
interface Tool { id: Id; unlock: Id[]; recipe: {ref: Ref; qty: number}[]; params: Record<string, unknown>; }
interface Entity { id: Id; cost: number; tolerance: number; speedTps: number; spawnFlux: number; behavior: Id;
  params: Record<string, unknown>; }
interface Stratum { id: Id; dMin: number; dMax: number; ambientZone: number; tiles: {id: Id; weight: number}[];
  spawnWeights: Record<Id, number>; }
interface Zone { id: Id; ambientColor: number; ambientStrength: number; darkRamp: number; terrainRamps: number[]; }
// params.json: time, flux, light, warp, buoyancy, attention, player, world, research (all GDD tuning values)

Reference implementations (behaviour the build must match):

• docs/sims/fluxcore.py: flux passes, proportional suppression, strain, light propagation, runoff drain direction.
• docs/sims/S05_research.py: generate(): recipe generation (seeded shuffle per tier, backtracking, pair uniqueness).

20.4 Milestones and acceptance criteria

M0 Foundations.

• The repo, CI, and the sim core (grid, ticks, RNG streams, commands, save and load).
• Palette and LUT build (lanternforge lut) and lanternforge v1 (clean, check).
• Accept: the determinism test passes (below), and lanternforge check passes on a fixture set.

M1 Surface slice (proves the promise).

• Contents: exactly the §19.3 manifest, delivered through checkpoints M1.1 → M1.3 (§19.4). The art pipeline runs end to end: procedural tiles, plus the Alembic generated by AI and cleaned with lanternforge. Until the owner supplies it (D41), use the synthetic AI-like stand-in.
• Acceptance (all required):
  1. Palette compliance: 100% of pixels in 100 sampled frames are palette colors (automated).
  2. Mood histogram for a reference shot of the default seed, at the house at night, with the hearth lit and one wisp lantern: ≥ 55% of pixels are R0/R1 shades 0–4; 2–10% are R2 shades ≥ 4; 0.5–5% are R3 shades ≥ 4 (automated).
  3. Reference match: a side-by-side contact sheet (reference image vs a game screenshot at the same framing) is approved by the project owner.
  4. AI sprite integration (re-run when the owner's real AI Alembic lands, D41): the Alembic, run through lanternforge, renders next to procedural tiles under 3 lighting setups (hearth only, wisp only, darkness with a pilot light). It passes lanternforge check, has the same outline rule as the tiles, and the owner can't single it out as "the odd one" in a blind 5-asset contact sheet.
  5. Research chain: a scripted bot identifies Glass in ≤ 3 tests, and each failure puts 40 motes into the world (automated).
  6. Automation: the Alembic distills 20 logs from a chest into jars without the player, emitting 40 motes in total (automated).
  7. Flux behavior: in the test scene, flux from the shed alembic reaches soil under the shed within 2 min; a Wisp Lantern holds a 3-alembic shed below 50 motes; with no lamp it passes 150 within 6 min (automated; values from S01 and S02).
  8. Gleaner fairness: with the shed dark and flux ≥ 150, a gleaner takes from the shed chest within 2 Nights, never spawns in view, and the stolen stack ends up in a midden that appears on the map (automated).
  9. Cozy + uneasy in ten minutes: with ≥ 3 first-time playtesters doing 10-minute sessions, the average is cozy ≥ 4/5 and uneasy ≥ 3/5, and at least 2 of 3 mention a specific unsettling observation unprompted.
  10. Performance: budgets in §20.2 hold on the reference machine.

M2 Depth I (fossil layer). Structure and integrity, shale cave-ins, beams, golems with chalk routes, keeper sites and journals, the Separator and Prism, arrangers and whisperers, the full weather model, and the reservoir. Accept: S04 world-gen stability holds over 1,000 seeds; the golem route test passes; the arranger restore test passes.

M3 Depth II (crystal layer). Buoyancy, the tide, taps and Resonance, augers, jettison, Lift Bladders, Crystal Lamps, tilt, dimmers, warp and hallucinations with all 6 tells, the Clarity Lens, and the Visitor. Accept: the buoyancy regression matches S03; the hallucination tells test passes (a hallucination never affects light, flux or reflections, or the log).

M4 Depth III (Roots and Heart). Root growth and shoving, Root Stakes, the Heart chamber, the three ending accumulators and endless modes, Foundering and Keeper Records. Accept: scripted saves reach each ending, and each accumulator responds only to its own conditions.

M5 Content, balance and polish. All compounds and blueprints, charters, balance passes against the S06 pacing targets, and accessibility.

20.5 Automated tests the build must have

1. Sim determinism: for seeds {1, 42, 1337, 2^31−1} and a recorded 10-minute command log, the state hash at ticks 1k, 5k and 12k is identical across runs, and identical between a Node runner and a browser runner.
2. Flux conservation: for 10,000 steps with random sources and sinks, Σflux(t) = Σflux(0) + emitted − (suppressed + absorbed by sinks + vented), exactly.
3. Flux regression: golden scenes (shed, shaft pooling, rain scrub, lamp strain) match stored per-cell snapshots at fixed steps.
4. Buoyancy regression: fixed islands with scripted crystal removal match the A_eq and tide table from S03 (±0 millifathoms).
5. Structure regression: golden dig scenarios (soil span 10 OK and 11 cracks; shale span 6/7; detach and fall) match.
6. World-gen invariants: over 1,000 seeds: zero cracking tiles; recipe validation (§6.1.3) passes; the pond holds 40–56 water cells; crystal count is 380–460.
7. Research solvability: for 1,000 seeds, the S05 solver identifies all compounds.
8. Palette compliance: every PNG in /assets uses only palette colors with binary alpha; rendered frames in Playwright are 100% palette.
9. Asset grid compliance: sprite dimensions match their declared sizes, and tiles are 8 × 8 (per frame).
10. Save/load round-trip: save, then load, then 1,000 ticks gives the same hash as running 1,000 ticks without the save.
11. Hallucination isolation: at W = 100 for 1 Night, the sim state hash matches the same run at W = 0 except for the warp fields and the RNG warp stream.
12. Entity fairness: across 100 seeded Nights, no entity spawns inside the camera rect, and none enters a cell with Ls ≥ its tolerance.
13. Data validation: at load, every /data file passes its zod schema and the docs/data/validate.py rules ported to TS (refs, pool tier rules, synthesis-only set, every essence used). CI fails on any problem.
14. Reference parity: the TS flux step and recipe generator reproduce fluxcore.py and S05 generate() golden outputs for 5 fixed scenes and seeds 0–99.

20.6 World generation (RNG stream worldgen; deterministic)

1. Seed parameters:
   • W0 ∈ [60, 76], depth D ∈ [172, 184], pond cells ∈ [40, 56], crystal tiles ∈ [380, 460];
   • keepers: Ansel, Tamsin and Ilse, plus 2 of {Odo, Bram, Merrit};
   • weather bias ±30% on the rain transitions.
2. Profile: for each rock row d, compute half-width hw(d) from §4.1, plus 1D value noise (period 12, amplitude 2) to get the solid span. Base tile by stratum band (strata.json). Mixes come from 2D value noise (period 6) thresholds on the weights: clay pockets in d 3–11, limestone lenses in fossil. Bone inclusions are stamped at 10% inside shale.
3. Surface:
   • Ground height is noise ±2 tiles (period 16), except a flat 16-tile house plateau left of centre and a pond basin right of centre (width = pond cells ÷ 2.5, depth 2–3) filled with water.
   • The grass layer goes on top.
   • Prefabs (tile maps in data/prefabs/*.json, authored in M1): house 12 × 6 with roof, hearth, bed, table, shelf, door and note; shed 8 × 5 with the broken alembic, chest and silverleaf seeds, placed 10–14 tiles from the house; garden plot 6 × 2; Lantern Tree at least 6 tiles from the house; ladder hatch.
4. Fossil caves: a cellular automaton on d 14–48 (45% fill, 4 iterations, born at 5+ and survives at 4+ of 8 neighbours). Keep pockets of 12+ cells. Keeper sites (a 6 × 4 prefab: skeleton, journal, cache, broken machine) go in the largest pockets, one per chosen lesson-keeper, plus Tamsin's workshop.
5. Crystal: random-walk veins (6–14 steps) seeded at x ~ Normal(centre, W0/6), d ~ Uniform(52, 98), plus 2–3 geodes (5 × 4 air lined with crystal). Repeat until the count is in [380, 460]. Carve the 18 × 6 crystal cavern at d 58–64.
6. Roots: an L-system of 6 primary roots growing up from the Heart chamber (step 1 tile, branch probability 0.15, length 40–60) converts stone to root-wood at d 100–150, plus dangling strands of 3–14 tiles below the bulb.
7. The Heart chamber: a 22 × 12 cavity at d 155–167 with a heartstone floor, the Heart object, and the three archetype remains.
8. Stability pass (§4.1): no natural tile with integrity < 20.
9. Spawns: lit hearth and 2 lanterns (1 lit), Wick on the rug, 2 wisps at the pond, 3 frogs.
10. M1 runs steps 1 and 3 and 9 only, on a 64-wide island with 12 soil and clay rows over bedrock.

20.7 Controls (mouse + keyboard; all rebindable; no hover-only information)

Hovering any world object for 0.4 s shows a tooltip. The same tooltip pins with Right-mouse held for 0.4 s, so it works without hover.

20.8 UI flows

• Title: Continue · New world (seed field with a random default, the Lost Ledger toggle) · Options · Quit.
• In game: the HUD (§15.1).
  • E opens the inventory (30 slots plus the essence satchel, which holds up to 64 drams of each essence) and, within 3 tiles of a workbench, its crafting list (only unlocked recipes).
  • Right-click a container or machine to open its panel beside the inventory: slots, pilot state in words, rate, flux per minute, fuel.
  • The Research Desk panel has two essence pickers (satchel plus jars within 3 tiles), a Test button showing the cost, and a link to the Ledger page.
  • R opens the Ledger: essence pages in M1, the Correspondence board from M2.
  • Esc pauses: Resume · Options · Save & quit.
• Saving: autosave at every Dusk-watch and on quit. 3 slots in IndexedDB, with export and import to a .lanternhold file.
• All panels are 9-slice parchment at 480 × 270 and never cover the player's own tile.

20.9 Entity navigation

• Passable cells per kind:
  • Gleaner (many-legged): any non-solid cell with a solid among its 8 neighbours, so it walks walls and ceilings.
  • Arranger: non-solid with solid below, or a ladder.
  • Dimmer: any non-solid cell.
  • Whisperer: never moves.
  • For all kinds, the cell's entity Ls must be < tolerance. Ward Stones force Ls 6 within 5 tiles.
• Flow fields: per entity kind and target set, BFS from targets (4-neighbour; 8 for dimmers), uniform cost. Recompute when a light-map change touches the field's bounding box, at most once per 5 s per field.
• Movement: cell to cell at the kind's speed, interpolated for rendering.
• Caught by light: if an entity's cell becomes Ls ≥ tolerance, it retreats back along its own path to the last dark cell. If none is within 3 cells, it dissolves and drops what it carries.
• Middens: the nearest dark air cell ≥ 20 tiles from every light source (tie-break: lowest y, then x). A midden is a 16-slot container marked "?" on the map. It persists until emptied.

20.10 Save format

• JSON header: version, seed, tick, night, RNG stream states, player, inventories, the satchel, machines and lamps (with their state machines), entities, golems, the Ledger (facts plus player marks), the Log, R, Taint.
• Binary chunks (base64 of deflated, run-length-encoded typed arrays): tile kind (u8), flux (u32), water (u8), crystal charge (u16, ×10⁻⁴), root state (u8).
• Light, integrity and flow fields are recomputed on load, never saved.
• version is an integer with pure migration functions vN → vN+1. A round-trip test is §20.5 #10.

20.11 Player physics (all in params.json › player)

• Collision AABB 6 × 14 px.
• Walk 40 px/s. Gravity 640 px/s². Jump velocity 180 px/s (about a 3-tile jump).
• Terminal fall speed 240 px/s. Coyote time 0.1 s. Climb 24 px/s.
• Automatic step-up onto 1-tile ledges while walking.
• Reach 5 tiles from the player's centre.
• Movement is resolved per axis against solid tiles; platforms are solid from above only.

20.12 M1 object behaviours (state machines)

• Hearth:
  • States: lit (warm 13), embers (warm 6).
  • Right-click with a log adds 6 min of fuel (store up to 30 min). Lit while fuel > 0.
• Candle and lantern:
  • States: lit, out, guttered.
  • Right-click with fuel refuels and relights.
  • Unroofed (sky-exposed) during rain: a 20%-per-rain-minute chance to go out (RNG stream weather).
  • The held lantern uses the player's lamp oil.
• Wisp Lantern: states empty, lit, fled. Right-click with a bottled wisp fills it. It flees per §6.3.6.
• Research Desk: a test consumes 2 + 2 drams from the satchel or nearby jars, resolves instantly, applies the flux burst at the desk's top cell, and records a fact.
• Alembic:
  • States: broken (leaks 1.2 AE; right-click with a Glass Bulb to repair), idle, working (6 s cycle), starved (no item or no fuel), blocked (an output tank is full).
  • Fuel slot: Ember drams from an adjacent jar, or solid fuel (1 log = 4 Ember-dram equivalents, 1 soot = 1).
  • Input: the adjacent chest, left-most slot first.
  • Output: per-essence internal tanks (16), which drain 1 dram/s into adjacent jars locked to that essence.
• Chest: 16 slots. A gleaner takes the left-most non-empty stack.
• Jar: 64 drams of one essence. The type locks when the first dram enters and unlocks when empty.
• Gleaner: states spawning (3 s fade) → seeking → taking (1 s) → fleeing to its midden → depositing → dissolving. It obeys §20.9.
• Wisps: spawn per §6.9.1, drift within 6 tiles of the pond with a sine bob, flee air flux ≥ 150. Catching one is a 1 s right-click hold with the net.
• Wick:
  • States: wander, sleep, follow, hiss.
  • Wanders lit cells within 12 tiles of the hearth and sleeps by the hearth in the Deep-watch.
  • Follows the player within 8 tiles while the player is in lit cells.
  • Hisses at real entities within 10 tiles.