World sounds are local: fade with distance and pan (distant sizzles snapped constantly)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/DESIGN.md

@@ -177,6 +177,12 @@ above, including:
 
 - **Fewer, smaller messages.** Molds show only a small percentage, red when blocked or spoiled and gold when a casting waits for F; details are in the hover panel. Bars dropping, blocked molds and set castings no longer pop up cards or toasts. Fan heat is a red marker on the fan; melted tubes and machines get a short red label where they were. Status lines are one short sentence. The owner found the messages too large and too many.
 
+- **World sounds are local.** Sounds from the world (water sizzling on hot metal or lava, and
+  any other event with a place) fade with distance from the view and pan left or right; they go
+  silent one screen width off-screen. The owner heard a constant snapping that followed the bot
+  in an older world but not in a new one. Most likely the sizzle: in a test, a lava and water
+  contact far from the bot sizzled about 580 times a minute, all played at full volume.
+
 ## Ideas not built yet
 
 - **Concrete**, as a stronger wall material from rubble.

docs/PROJECT_MAP.md

@@ -354,9 +354,9 @@ Smooth look: a WebGL2 pass that turns the per-grain buffers drawWorld fills (col
 - functions: smCompile, smoothAvailable, smUpload, smoothDraw, smoothPace
 - variables: SM, SM_VS, SM_FS, smBytes
 
-### src/ui/audio.js (209 lines)
+### src/ui/audio.js (228 lines)
 Audio: chiptune effects and generative music that changes with depth. Everything is synthesized with WebAudio, no samples.
-- functions: auInit, auVolumes, rateOk, tone, noiseBurst, playSfx, auAmbient, mtof, zoneForDepth, scaleNote, musicScheduler
+- functions: auInit, auVolumes, rateOk, tone, noiseBurst, sfxPlace, playSfx, auAmbient, mtof, zoneForDepth, scaleNote, musicScheduler
 - variables: AU, SFX, ZONES
 
 ### src/ui/state.js (67 lines)

docs/agent-log.md

@@ -4,6 +4,23 @@ What agents have done, newest first. Add an entry for every piece of work: the d
 note or request it was for, what changed, the files touched, the tests run, and anything left
 open or not verified. Keep each entry short; the git history has the details.
 
+## 2026-10-23: world sounds are local (Claude Code, with Codex)
+
+Note: "there is a sound effect that seems to happen randomly but constantly… maybe the sound
+effects are not local?" The owner then confirmed a new world is quiet.
+
+- Measured headlessly over 5 game minutes: a fresh world emits no sounds; a lava and water
+  contact 720+ grains from the bot emitted 2,889 sizzles (about 580 a minute), and `events.js`
+  played every one at full volume. The sizzle (`heat.js` boiling and quenching) is the only sim
+  sound with a position.
+- `src/ui/audio.js`: `sfxPlace(x, y)` gives gain (1 in view, 0 one view width beyond it) and
+  pan; `playSfx(name, arg, x, y)` skips silent ones before the rate limit and plays the rest
+  through a gain and stereo panner (`AU.bus`). `src/ui/events.js` passes positions.
+  `docs/DESIGN.md`, `docs/PROJECT_MAP.md`.
+- `test/play.py`: far off-screen is silent, on screen plays, just off-screen is quieter and
+  panned. All 11 headless suites, `play.py` and `t_smooth.py` pass.
+- Open: not tested against the owner's own save; the owner checks by ear.
+
 ## 2026-10-23: fewer, smaller messages (Claude Code, with Codex)
 
 Note: "lets change the engot mold and other status messages. they are way too large and just too