Briefs: Headshell Workshop (cartridge assembly) + Glow-Up art pass

Fresh-eyes review outcomes as two parallel-safe Opus briefs:
- WORKSHOP_CARTRIDGE.md: the stylus node becomes a five-stage cartridge
  assembly - seat/rotate the cart, crimp four color-coded wires onto
  stubborn pins (catenary carry, continuity lamp), torque screws evenly
  (tilt = azimuth error), balance the counterweight while RIDING the
  seesawing tonearm, then a needle-drop test where every mistake is
  audible + drawn on a diegetic scope. Multiplayer-shared state.
- GLOWUP_ART.md: atlas v2 (32px, tile variants), selective LED bloom,
  screen-print decals + party flyers, mixer-face density, PCB pagodas.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

docs/briefs/GLOWUP_ART.md

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+# BRIEF — The Glow-Up (art & atmosphere pass)
+
+*Fresh-eyes verdict: the bones are great, the surfaces are underdressed.
+This pass closes the gap to the concept art. Pure art/atmosphere — no
+gameplay logic — so it can run in parallel with WORKSHOP_CARTRIDGE.md.*
+
+**For one Opus 4.8 session.** Read `docs/CONTRACTS.md`,
+`docs/INTEGRATION_NOTES.md`, `src/engine/atlas.ts`, `src/engine/renderer.ts`,
+`src/worldgen/buildBooth.ts`, `src/fx/` first.
+
+**You own:** `src/engine/atlas.ts`, `src/engine/renderer.ts`,
+`src/worldgen/**` (dressing additions), `src/fx/**` (decals module),
+`src/ui/Menu.ts` (one settings row). **Merge point with the workshop
+brief:** `src/main.ts` and `src/worldgen/buildBooth.ts` — keep your edits
+small and additive there. Do not touch `src/machines/**`, `src/interact/**`,
+`src/audio/**`, `src/net/**`, `server/**`.
+
+## Findings this brief fixes (from the review, with screenshots taken)
+
+1. **Mixer face is an empty black plain** — knob clusters are specks on a
+   82×95 desert; real DJMs are dense. No screen-print labels anywhere.
+2. **PCB Depths read as green wallpaper** — one tile repeated makes
+   astroturf, not circuitry; caverns lack vertical interest.
+3. **Textures are flat at 16px** — brushed_alu reads as concrete speckle
+   up close; vinyl tiers are matte plastic; no tile variation anywhere.
+4. **LEDs don't bloom** — emissive blocks read as flat colored squares;
+   the concept art's glow is absent.
+5. Fader alleys/vents are void-black slots with no depth cues.
+
+## Tasks
+
+### G1. Atlas v2 (engine/atlas.ts)
+- Tiles 16→**32 px**, and give patterns **per-block-position variation**:
+  hash (x,y,z) → one of up to 4 painted variants per pattern (requires
+  the mesher's UV path to pick a variant — if that's invasive, an
+  acceptable fallback is 4 variants painted for `pcb` only, chosen by a
+  world-position hash in the shader patch; document your choice).
+- Pattern quality: `brushed` = long directional strokes (not noise);
+  `grooves` = concentric arcs with a subtle specular line; `pcb` = 3–4
+  variants that visually tile into routed traces + via dots + silkscreen
+  flecks; `plywood` = longer wavy grain, end-grain variant for `ply_edge`.
+- Keep `NearestFilter` chunkiness — sharper *pattern*, same voxel soul.
+- Material feel: give the two chunk materials a slightly higher
+  `envMapIntensity`-free polish via roughness tuning only (no env maps).
+
+### G2. Bloom (engine/renderer.ts + main.ts + Menu)
+- Selective bloom for emissive: `EffectComposer` + `UnrealBloomPass`
+  (three/examples), threshold tuned so ONLY LEDs/strobe/lamps bloom
+  (~strength 0.55, radius 0.4). This is the single biggest step toward
+  the concept art.
+- Gate on quality: add a `bloom` boolean to Settings (default on;
+  auto-off when quality = 'fast'). `createRenderer` returns a `render()`
+  that internally uses the composer when enabled — main.ts keeps calling
+  `render()` unchanged apart from passing the setting through.
+- Budget: ≥ 100 fps must survive on the current test machine; measure
+  before/after and record numbers in your handoff.
+
+### G3. Screen-print decal system (fx/decals.ts + worldgen anchors)
+- A tiny module that bakes text/markings onto canvas textures applied as
+  thin plane meshes (0.05 proud, `polygonOffset` to avoid z-fight).
+- Print set (all positions derived from LAYOUT/anchors):
+  - Mixer face: `CH 1–4` under each fader alley, tick marks along alleys,
+    `TURNCRAFT-800` model text at the top edge, crossfader `A ↔ B`.
+  - Decks: `START·STOP`, `33` `45` beside buttons, pitch `+/−` scale,
+    Technics-style script line on the plinth rear ("Quartz Direct Drive").
+  - Patch bay: tiny socket numbers. Fuse box: `FUSE 250V`.
+  - Booth walls: 3–4 procedural **party flyers** (canvas typography:
+    random gig names from a word bank, big condensed type, one accent
+    color each) pasted like posters near the patch bay and front lip.
+- Keep total decal draw calls < 25 (merge planes per gear piece where easy).
+
+### G4. Worldgen density pass (buildBooth.ts — additive only)
+- **Mixer face**: mushroom knob caps (2×2 cap on 1×1 stem, mixed heights)
+  replacing the flat single-voxel caps; double the knob rows per channel
+  strip (EQ + trim + filter row); 1-voxel panel seam grooves (matte_black
+  → rubber lines) sectioning the face; LED pips beside each alley.
+- **PCB Depths**: IC-chip **pagoda buildings** (matte_black slabs on
+  solder pin-legs you can walk under, 2–3 sizes, a few stacked), ribbon
+  cable walls (alternating cable_black/cable_white columns), more copper
+  trace inlays connecting features, sparse led_green "status" pips near
+  ICs (they pulse post-win via existing emissive boost — free).
+- **Fader alleys/vents**: a dim led_amber pip at the bottom of each alley
+  and inside vent mouths so dark slots read as *deep*, not void.
+- Keep `buildBooth` deterministic (same seed), build time < 800 ms, and
+  do NOT move any LAYOUT/QUEST_POS anchor (machines depend on them).
+
+### G5. Record material moment
+- The vinyl tier sides get a subtle groove-sheen: a fine repeating
+  light/dark ring texture on the tier side cylinders (machines/platter.ts
+  is workshop-owned — instead provide the improved texture via
+  `blockMaterial`'s existing tint path or hand the workshop session a
+  `recordSideTexture()` in `src/fx/decals.ts` and note it in your handoff
+  for them to wire — do not edit platter.ts yourself).
+
+## Acceptance
+
+- [ ] Before/after screenshots of: mixer face, PCB depths, deck top,
+      full-booth win state (use `window.TURNCRAFT_CINE`)
+- [ ] Bloom on LEDs only (plywood must NOT glow), toggleable, fps ≥ 100
+      measured and recorded
+- [ ] All decals legible at play distance, no z-fighting while circling
+- [ ] buildBooth deterministic, anchors untouched (grep QUEST_POS usage),
+      build < 800 ms, chunk meshes < 600
+- [ ] `npm run typecheck` clean, zero console errors, live smoke of the
+      full quest still passes (don't break the game for prettiness)
+- [ ] Handoff note listing every file touched + the two merge points
+
+## Out of scope
+
+Mobs/critters, mobile UI, new blocks (atlas is at 31/32 ids — variants
+must come from painting, not new ids), any machines/audio/net code.

docs/briefs/WORKSHOP_CARTRIDGE.md

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+# BRIEF — The Headshell Workshop
+
+*Expands the `stylus` quest node from a 30-second fetch into the game's
+centerpiece: a full cartridge assembly — four stubborn wires, alignment,
+screws, and balancing a tonearm you're standing on.*
+
+**For one Opus 4.8 session.** Read `docs/CONTRACTS.md`, `docs/DESIGN.md`,
+`docs/INTEGRATION_NOTES.md` and skim `src/machines/tonearm.ts`,
+`src/machines/faders.ts` (the push-sled mechanic you'll reuse),
+`src/interact/interaction.ts`, `src/audio/AudioEngine.ts`, `src/ui/Hud.ts`,
+`src/net/NetClient.ts`, `server/relay.mjs` before writing code.
+
+**You own:** new `src/machines/workshop/**`, plus surgical edits to
+`src/machines/tonearm.ts`, `src/interact/interaction.ts`,
+`src/audio/AudioEngine.ts` (additive methods only), `src/ui/Hud.ts`
+(additive), `src/worldgen/buildBooth.ts` (workbench dressing only),
+`src/net/NetClient.ts` + `server/relay.mjs` (one new message type),
+`src/core/events.ts` (adding `workshop:*` events is sanctioned — keep them
+additive), `src/main.ts` (wiring). Do not restructure existing systems.
+
+## Why this design
+
+Real headshell assembly is: 4 colored tag-wires onto tiny cartridge pins,
+cartridge aligned square in the shell, two screws tightened evenly, then
+counterweight balancing for tracking force. It's fiddly for full-size
+humans. At 7 mm tall it's *civil engineering* — and every real-world
+failure mode has an **audible** consequence, which is this game's language:
+sound is the win state.
+
+Design laws:
+1. **Nothing hard-fails.** Every mistake is visible/audible and reversible.
+2. **Diegetic feedback.** A continuity lamp, a bubble level, and a scope
+   block tell you what's wrong — no tutorial text walls.
+3. **Every stage is multiplayer-shared** — two players can split the work.
+
+## The five stages
+
+State machine `WorkshopState` (authoritative shape, also what syncs):
+
+```ts
+interface WorkshopState {
+  cartSeated: boolean;
+  cartRotation: 0 | 1 | 2 | 3;     // quarter turns; 0 = correct (stylus forward)
+  wires: (0 | 1 | 2 | 3 | null)[]; // wire i (R,W,G,B) -> pin index or unattached
+  screws: [number, number];        // 0..1 torque each
+  weightNotch: number;             // 0..10 along the arm; 7 = zero-balance, 8 = 2g target
+  tested: boolean;                 // last needle-drop was clean
+}
+```
+
+### Stage 1 — Seat the cartridge
+- The existing parts-bin chrome pickup **becomes the cartridge** (rename in
+  help text; same block item 11, same carry flow).
+- At the tonearm pedestal (Deck A), the arm rests in a **service clip**:
+  add a `rest_clip` visual on the pedestal and a new Tonearm state
+  `'service'` — arm parked low over the pedestal, headshell at
+  player-reachable height (~`Y_PLINTH_TOP + 3`), colliders inert.
+- `use` with the cartridge on the headshell (existing route in
+  `interaction.ts`) now **seats** instead of instantly repairing: consume
+  the item, spawn the cartridge body visual (a chunky box ~4×2.5×3 with a
+  cantilever + needle tip) in a **random wrong rotation** (1–3).
+- E on the seated cartridge cycles rotation 90°. Correct orientation:
+  needle tip glints (small emissive flash) + a soft click. Wrong is
+  allowed — it just can't pass the needle-drop test.
+
+### Stage 2 — The four wires (the iconic bit)
+- A **wire loom** stands on the pedestal (new worldgen dressing: a small
+  spool rack). Four tag-wires hang from it: red, white, green, blue.
+- The cartridge back is a wall with **four pin posts**, color-capped:
+  R+ red, L+ white, R− green, L− blue — but shuffled physically (pin
+  *positions* are fixed per world; color caps tell you the truth).
+- Mechanic: E on a wire end → you're **carrying the wire**; a rendered
+  catenary line (THREE.Line, ~12 segments, sag by distance) trails from
+  the loom to your hand. Walk to a pin, **hold E 1.2 s** to crimp it on —
+  the hold has a wiggle animation (the pin is stubborn). E on an attached
+  wire pulls it off again. Any wire can go on any pin.
+- **Continuity lamp**: a 4-LED strip block on the loom rack; LED *i*
+  lights green when wire *i* is on its correct pin. (Solvable by sight.)
+- Carrying a wire caps jump velocity at half (the wire tugs) — release to
+  climb. Dropping (walking > 30 voxels away or pressing Q) returns the
+  wire to the loom.
+
+### Stage 3 — Screws
+- Two screw posts sit beside the shell slots. **Hold E** on a screw to
+  torque it: a radial HUD meter (new Hud element, bottom-center) fills
+  0→1 over ~2.5 s. **Shift+hold E** backs it off.
+- Balance rule: if `|screws[0] − screws[1]| > 0.4` while either is > 0.3,
+  the cartridge **visibly tilts** toward the tighter side + a creak SFX.
+  Finishing tilted (both ≥ 0.9 while tilted) = azimuth error (test
+  consequence below). Even torquing squares it up with a satisfying CLUNK.
+
+### Stage 4 — Balance the arm (the showstopper)
+- E on the cue lever releases the arm from the service clip → it becomes a
+  **live seesaw**: tilt angle driven by `weightNotch` vs the (now
+  cartridge-laden) head mass. Tail-heavy → arm tips back; nose-heavy →
+  needle dives.
+- The **counterweight is a push-sled** (reuse the Fader mechanic on a rail
+  along the arm tube, 11 notches): walk into it to shove it. The arm is a
+  kinematic collider chain that **tilts in real time under your feet** —
+  the player typically stands ON the arm while doing this. Physics: update
+  the arm segment colliders' transforms per tick from tilt; Lane B's
+  min-penetration cylinder/aabb resolution handles the ride (see
+  `INTEGRATION_NOTES.md` physics section — verify no slingshot on tilt).
+- **Bubble level**: a block on the pedestal with an emissive dot that
+  drifts left/right of center with tilt; centered = zero balance
+  (`weightNotch === 7`). One more notch (8) = correct 2 g tracking force
+  (detent click + the dot settles into a marked ring). 9–10 = too heavy.
+  ≤6 = too light.
+
+### Stage 5 — Drop the needle (the test)
+- E on the cue lever again: arm swings over the (must-be-spinning) record
+  and drops. A **test signal** plays — implement
+  `AudioEngine.playTestSignal(errors: TestErrors)`: a bare kick+bass loop
+  routed through an error chain:
+  - `swapLR` (R/W wires crossed with G/B partners): hard pan flip —
+    ping-pong the kick L/R so it's obvious.
+  - `phaseCancel` (a +/− pair swapped): invert one channel + collapse to
+    mono momentarily — thin, hollow, "wrong" sound.
+  - `azimuthTilt` (screws uneven): one channel −12 dB + light distortion
+    (waveshaper).
+  - `trackingLight` (notch ≤ 6): stutter — gate the signal 80 ms on/off
+    randomly + arm visibly bounces.
+  - `trackingHeavy` (notch ≥ 9): lowpass 1.2 kHz + platter rpm sag −15%
+    (temporarily scale the platter's target omega).
+  - Rotation wrong: needle skates — arm slides straight to the spindle
+    with a zip SFX, test aborts.
+- The **scope block** near the pedestal (canvas-textured face, ~6×4)
+  draws the verdict: clean sine when perfect; recognizable glyphs per
+  error (mirrored trace = swap, thin double line = phase, sagging line =
+  heavy…). Also emit `workshop:test` with the error list so the HUD
+  subtitle names the problem ("LEFT AND RIGHT ARE SWAPPED").
+- All clean → `quest.repair('stylus')` (existing event does the rest:
+  stem unlock, LED trace), plus a confetti burst of tiny screws (reuse
+  `Burst`), and the workshop machines lock into their final pose. The arm
+  then behaves exactly as the pre-existing tonearm (cue/track/return).
+
+## Multiplayer
+
+- One new message both ways: `{ t: 'workshop', s: WorkshopState }` —
+  last-write-wins, relayed and stored on the server beside `platters`
+  (validate: shape, enums, numbers in range). Late joiners get it in
+  `hello.state`.
+- `NetClient`: send on any local state change (reuse the `applyingRemote`
+  guard pattern); apply remote by calling `workshop.setState(s)` which
+  diffs and animates.
+- If `repaired.stylus` is already true on join, the workshop spawns in
+  its completed pose (cart seated, wires on, weight at 8).
+
+## Quest gating changes
+
+- The `stylus` node's help text changes (Menu HELP_HTML): "…find the
+  cartridge in the parts bin, then assemble it at the Deck A workbench —
+  wires, screws, balance. The lamp, the bubble and the scope will tell
+  you what's wrong."
+- Power-switch gating (`canPowerOn`) is unchanged — `stylus` just takes
+  honest work now.
+
+## Acceptance (verify each in a live browser, and two-tab the sync)
+
+- [ ] Full assembly happy-path completes and repairs `stylus`; ~5 min
+      first time, all stages revisitable
+- [ ] Each of the 6 error modes is audible AND readable on the scope, and
+      fixable without restarting
+- [ ] Standing on the arm while pushing the counterweight: the seesaw
+      tilts under you with no physics explosions (test at 33 AND stopped)
+- [ ] Wire carry: catenary renders, jump-cap applies, Q/distance returns it
+- [ ] Two tabs: one attaches wires while the other torques screws; states
+      converge; joiner sees mid-assembly state correctly
+- [ ] Completed-workshop pose on join when stylus already repaired
+- [ ] `npm run typecheck` clean; zero console errors in a full session;
+      relay validates the new message (fuzz: bad shapes dropped)
+- [ ] Update `docs/INTEGRATION_NOTES.md` with a short section + any
+      contract additions listed
+
+## Out of scope
+
+Deck B's arm (stays pre-assembled), anti-skate dial (stretch note only),
+mobile input, any rework of existing quest nodes.