# Lane C — World Builder · HANDOFF

**Status: complete.** `npm run typecheck` clean, demo runs with no console errors,
build is deterministic and fully validated (see below).

---

## Glow-Up G4 — worldgen density pass (2026-07-14)

Implemented the `src/worldgen/**` slice of `docs/briefs/GLOWUP_ART.md` (task G4).
The atlas (G1), bloom (G2), decals (G3) and record texture (G5) are engine/fx work
and are NOT in this lane — left for their sessions.

**Files touched (this pass):** `src/worldgen/buildBooth.ts`,
`src/demo/worldgenDemo.ts`. Nothing else.

**Merge points (shared with the Workshop session):** only `src/worldgen/buildBooth.ts`
(main.ts is untouched here). My edits are confined to `buildMixer`, `buildUnderTable`
(+ new `pagoda`/`buildPcbDetail`), and the deck-vent loop — all disjoint from the
Workshop brief's *Deck A pedestal* "workbench dressing", so a merge is clean.

**What it adds (additive; every pre-existing zone stays byte-identical):**
- **Mixer face** — dense mushroom knobs (1×1 stem + 2×2 cap, mixed heights, 6 rows ×
  3 cols × 4 channels, club-mixer palette) replacing the sparse specks; flush rubber
  **panel-seam grooves** sectioning the four channels; amber/green **LED depth pips**
  at each fader-alley floor and flanking; an amber glow behind each speaker-mesh vent.
- **PCB Depths** — walk-under **IC-chip pagodas** (matte_black slabs on solder pin-legs,
  stacked tiers, copper pin-1 dot, green status LED), **ribbon-cable walls** (deck rooms),
  extra copper trace inlays. Kept ≥15 voxels clear of every quest pickup.
- **Deck vents** — an amber pip at each shaft bottom so the drop reads as deep.

**Determinism:** the mixer detail is index-based (no `rng()`), and `buildPcbDetail` uses
its OWN seed (`WORLD_SEED ^ 0x9e3779b1`), so the main PRNG stream is untouched and all
other zones are identical. Two full builds are byte-identical (verified headless).

**Anchors:** no `LAYOUT`/`QUEST_POS` value moved. All 8 quest anchors still land on the
correct block (re-verified). Build 21–30 ms (« 800 ms budget). Chunk count unchanged.

**One demo fix:** the concept-art pass added an intentional shallow well step-ring
(outside `PLATTER.radius`); my old "well empty" assertion checked the full well and went
red. Retitled to **"platter footprint clear"** and scoped to `PLATTER.radius` — the region
Lane D's platter actually needs. Green again.

**Note (not mine to fix):** at this checkpoint the shared tree briefly failed global
`tsc` on the Workshop session's in-progress `src/audio/testSignal.ts` (a
`Float32Array<ArrayBuffer>` generic mismatch); it cleared on their next save. My files
typecheck clean in isolation.

---


## Public API surface (import from `src/worldgen`)

```ts
buildBooth(world: IVoxelWorld): void          // writes the ENTIRE static diorama
buildShell, buildDeckA, buildDeckB, buildMixer, buildCableCanyon,
buildPatchBay, buildUnderTable                // individually testable sub-builders
SPAWN: Vec3                                    // deck A plinth top, faces the mixer
SPAWN_LOOK: Vec3                               // suggested look-at (mixer face centre)
WORLD_SEED = 1210                              // fixed seed → identical booth every run
QUEST_POS: QuestPositions                      // {stylus,rca,crossfader,fuse,power} for Lane D
QUEST_REACH_POINTS, hasAdjacentAir(w, p)       // reachability helpers (used by the demo)
DECK_A, DECK_B, MIXER, UNDER, PATCH, RCA_SOCKET, RCA_PLUG  // LAYOUT-derived anchors
```

## What's done

Every zone in DESIGN §4 is built and visually confirmed in `demo-worldgen.html`:
shell + tabletop (front lip, vent slots, crate hatch + stair), both steel-grey
plinths (feet, alu border, **empty platter well** + chrome spindle stub, start/stop
+ 33/45 recesses, pitch canyon w/ green detent, tonearm base pedestal, strobe lamp),
Deck B dust drifts + half-open glass dust cover, the mixer massif (body, speaker-mesh
climb vents, 4 channel strips = knob-stem grids + **empty fader alleys**, crossfader
tram with the dust-jam plug, two VU towers, power-switch recess, fuse chimney), the
cable canyon (5 splined RCA/power cables to the patch bay + the quest cable ending
short with a loose gold plug + power strip), the patch-bay wall (alu panel, 2×6 gold
socket grid, the **empty quest socket** with red blink, two doorway rooms w/ copper
busbars + blue glow), and the PCB Depths (green board floors, copper traces, capacitor
pillars, solder stalagmites, sparse LEDs, the fuse box with a blown fuse, the parts
bin holding the fresh-fuse + stylus pickups, and the record crate of blue/black vinyl
slabs on edge with a leaning-slab ramp).

## What's intentionally NOT built (yours, Lane D)

The moving parts sit in the sockets I left for them: the **rotating platter/record**
(the empty circular well, radius `PLATTER.radius+2`, 6 deep, spindle stub at bottom),
the **tonearm arm + headshell** (base pedestal + empty socket anchor), the **fader
caps/sleds** (empty alley slots + crossfader tram), and the **buttons/switches**
(start/stop, 33/45, power — all left as recesses). Read `QUEST_POS` for exact voxels.

## Quest anchor convention (important for Lane D)

Each `QUEST_POS` voxel is a **reachable interaction anchor** (has an adjacent air
voxel — validated). Semantics per node:
- `stylus.socket` — empty voxel on the Deck A tonearm pedestal; drop the stylus here.
- `stylus.pickup` — the chrome stylus block in the parts bin (blue-spotlit).
- `rca.socket` — empty gold ring on the patch-bay wall face (air; push the plug in).
- `rca.plug` — the loose gold plug lying on the canyon floor (top is open air).
- `crossfader.jam` — **top-centre** of the dust plug in the tram (mine downward).
- `fuse.box` — the blown fuse (rubber block, chrome caps) in the wall fuse box.
- `fuse.pickup` — the fresh fuse (glass + chrome caps) in the parts bin.
- `power.switch` — recess on the mixer rear top (dark until the other four are done).

## Validation (headless + in-demo + cross-lane, all green)

build 14 ms (< 500) · deterministic (two runs byte-identical) · **0** OOB writes ·
both platter wells empty · spawn on solid steel with headroom · **8/8** quest points
reachable · fuse/stylus anchors land on the intended block · record crate populated ·
29/30 non-air block types · ~4.5 M non-air voxels (24.6% fill).

**Cross-lane smoke test** (buildBooth against Lane A's real `VoxelWorld`, not a mock):
`fillBox` fast path ENABLED · 30.7 ms build · all acceptance checks still pass.

## Post-review fixes (adversarial multi-agent pass, all verified)

- **[HIGH]** record crate placed **zero** vinyl slabs (footprint collapsed to ~2 voxels
  because it was bounded by `deckA.minX`); re-anchored to the open under-ledge volume in
  front of Deck A — now 8–9 records on edge. Added a regression guard.
- **[MED]** `QUEST_POS.fuse.box` pointed at the alu frame, one voxel off the fuse; the
  blown fuse now sits **exactly** at that anchor (frame moved behind). Guarded.
- **[MED]** VU-tower LED ladders were sealed inside a closed casing; the front (DJ-facing)
  face is now open so the meters read.
- **[LOW]** added the "resistor beams" the brief lists for the PCB rooms.
- **[LOW]** the demo's "Record Crate" teleport aimed at `x=12` (inside the left plywood
  wall) and at the crate's old location; re-aimed at the crate's real centre.
- (A `fillBox` doc-comment nit was a false positive; tightened it regardless.)

## Contract friction / notes for the integrator

1. **Mixer height.** The brief says "tabletop → `topY`+40", but `constants.ts`
   (`mixer.topY = 67`, "27 voxels tall") and DESIGN §3 both put the mixer face plate
   TOP surface at `topY = 67`. I built to **face-plate-top = 67** (body 40–66) with a
   raised rear ridge + 12-tall VU towers for the "tallest mesa" silhouette. If the
   design truly wanted a 107-tall mixer, that's a one-line change in `buildMixer`.
2. **`fillBox` fast path — RESOLVED.** `tools.box()` uses
   `world.fillBox(x0,y0,z0,x1,y1,z1,id)` (INCLUSIVE bounds) if present, else a
   `setBlock` loop. Confirmed against Lane A's shipped `src/engine/VoxelWorld.ts:117`:
   the signature and inclusive-clamp semantics **match exactly**, so the fast path
   engages at integration (verified — see cross-lane smoke test above). No action needed.
3. **Elevation model.** A `Y_*` constant is the TOP-SURFACE PLANE: the topmost solid
   block of that stratum is at index `Y_*-1`; blocks placed on the surface sit at
   `Y_*`. Documented in `anchors.ts`. Platter well is carved 6 down from `Y_PLINTH_TOP`
   so Lane D's platter (top at `Y_RECORD_TOP=85`) rises cleanly out of it.
4. **No duplicated coords.** Every spindle/mixer/patch-bay position derives from
   `LAYOUT` via `anchors.ts` (single source). Lane D should read positions from
   `QUEST_POS` / the exported anchors, never re-hardcode.
5. **Structural blocks are `breakable:false`** already in `blocks.ts` (plywood, cables)
   — the booth keeps its shape; nothing here relies on that beyond honoring it.