A loaded world starts around the player first, the rest a few areas a tick (t21)

- Areas within 150 grains of the bot start at once; the others 12 a tick, nearest first, and any
  the bot flies toward start straight away. A Huge world is fully started after 17 s.
- Huge world, first 600 ticks: average 15.2 -> 5.5 ms/tick, worst 79.7 -> 16.2.
- New test/t_load.js.

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

docs/DESIGN.md

@@ -358,6 +358,12 @@ above, including:
   still sleep. Through burning fuel sinking stays at the old slow pace: furnace beds are tuned to
   it, and dirt heaped on a burning pile must smother it into charcoal rather than sink through.
 
+- **A loaded world starts around the player first (t21, 2026-10-25).** Loading used to start every
+  area of the world at once, and a Huge world then took 15 ms a tick for its first 10 seconds,
+  with ticks up to 80 ms. Now the areas within 150 grains of the bot start at once, the rest 12 a
+  tick, nearest first (a Huge world is fully started after 17 s), and flying toward areas still
+  waiting starts them. Nothing is skipped: the same settling happens, spread out.
+
 ## Ideas not built yet
 
 - **Concrete**, as a stronger wall material from rubble.

docs/PROJECT_MAP.md

@@ -220,10 +220,10 @@ Starter furnace designs and the milestone list shown in the notebook.
 - functions: smelterBlueprint
 - variables: STARTER_DESIGNS, MILESTONES
 
-### src/sim/world.js (102 lines)
+### src/sim/world.js (104 lines)
 World state: the per-cell typed arrays, alloc(), ambient temperature by depth, waking.
 - functions: emit, bagCap, discover, alloc, depthU, depthY, meanSurface, computeAmbient, fillNoise, wakeXY, wakeHeatXY, wakeIdx, wakeHeatIdx
-- variables: W, H, N, CW, CH, NCH, mat, temp, life, flags, stamp, part, mach, digp, noiseB, airS, netId, isPow, occ, surfY, dirtY, graniteY, basaltY, magmaY, roofY, AMB, worldSeed, surfBase, underD, shallowD, lapse, BW, BH, NB, blockP, blockV, ents, bgm, flyers, ghostBlocks, ghostMolds, awake, hot, hotLvl, powderArea, roofDirty, tick, tickStamp, machines, molds, nets, pcells, powerDirty, beltL, beltR, tubeLists, brokenMachines, ghostMachines, ghostBlocked, EV, bot, bag, bagTotal, player, seen, ledger, stats
+- variables: W, H, N, CW, CH, NCH, mat, temp, life, flags, stamp, part, mach, digp, noiseB, airS, netId, isPow, occ, surfY, dirtY, graniteY, basaltY, magmaY, roofY, AMB, worldSeed, surfBase, underD, shallowD, lapse, BW, BH, NB, blockP, blockV, ents, bgm, flyers, ghostBlocks, ghostMolds, awake, hot, hotLvl, powderArea, roofDirty, loadWakeOrder, loadWakePending, loadWakeIndex, tick, tickStamp, machines, molds, nets, pcells, powerDirty, beltL, beltR, tubeLists, brokenMachines, ghostMachines, ghostBlocked, EV, bot, bag, bagTotal, player, seen, ledger, stats
 
 ### src/sim/fog.js (52 lines)
 Exploration only: never changes grains or the random stream.
@@ -329,7 +329,7 @@ Weather: clouds from steam, rain and snow, and the world water count.
 - functions: wrnd, resetWeather, rainGap, worldWater, absorbSteam, spawnRain, rainAt, weatherTick
 - variables: WBAND, WS, weather
 
-### src/sim/tick.js (27 lines)
+### src/sim/tick.js (28 lines)
 simTick: one simulation step, in order.
 - functions: simTick
 
@@ -342,9 +342,9 @@ World generation helpers: noise and removal of tiny hard rock specks.
 World generation: staged terrain, ore, caves and placement, with synchronous and async entry points.
 - functions: generateWorld, generateWorldAsync
 
-### src/sim/save.js (141 lines)
+### src/sim/save.js (177 lines)
 Saving and loading a world (serializeWorld / deserializeWorld) and old-save migration.
-- functions: serializeWorld, deserializeWorld
+- functions: serializeWorld, deserializeWorld, startLoadWake, wakeLoadArea, wakeLoadNearBot, loadWakeTick
 - variables: SAVE_VERSION, TOFF
 
 ### src/render/setup.js (200 lines)
@@ -509,6 +509,7 @@ The frame loop and boot.
 - `test/t_econ.js`: Economy: the dock (instant sale), orders, prices, the market dip, money for machines, alloys.
 - `test/t_fog.js`: Fog: surface, sight, range, saves and simulation independence.
 - `test/t_furnace_repeat.js`: The starter furnaces keep working when fired again and again without cleaning, however the charge goes in: mixed, ore first with coal on top, or blown in through the vent. Each case plays furnace_play.js, which builds the design and fires it like a player.
+- `test/t_load.js`: Reload wakes nearby areas first, without losing distant water, fire or saved state.
 - `test/t_molds.js`: Molds and furnaces stay usable: ingots drop below and keep their stubs, plugs over molds are cleared, spoiled castings can be knocked out, grains never drop through a grate by teleporting, and slag lets the fire breathe.
 - `test/t_physics.js`: Sand and other powders, molten metal and gases: heaps, sorting, sinking, setting, rising and fading. Water has its own suite (t_water.js). Tall worlds keep geothermal heat out of the way.
 - `test/t_pipes.js`: Pipes, pumps and outlets move liquids; the Grinder grinds waste rock for trace ore.

docs/agent-log.md

@@ -4,6 +4,18 @@ 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.
 
+## 2026-10-25: t21: a loaded world starts around the player first (Claude Code, Codex)
+
+- Owner: "lets speed up the first load speed. load in areas around the player first".
+- `src/sim/save.js`: `deserializeWorld` no longer wakes every area; `startLoadWake()` keeps the
+  load-time heat scan's result per area, wakes those within 150 grains of the bot, and queues the
+  rest by distance; `loadWakeTick()` (from `simTick`) wakes 12 a tick and, every 8 ticks, any still
+  waiting within 150 grains of the bot. The queue is not saved.
+- Huge world, ms/tick before -> after: ticks 0-600 average 15.2 -> 5.5, max 79.7 -> 16.2, 95th
+  percentile 21.0 -> 11.0; ticks 600-1800 average 7.3 -> 10.0 (the same work, later). Every area
+  has started by tick 1024 (17 s).
+- `test/t_load.js` (19 checks). `run_all.py --browser` ALL PASSED.
+
 ## 2026-10-24: t21 phase 4: duplicates merged, largest files split (Claude Code, Codex)
 
 - Merged seven real duplicates: wall refunds (`removeWallCell`, walls and molds), tube edges and