One clock for every land: going back to a land catches it up on the time away (like a night's sleep) instead of rewinding to when you left; J3 decided: a server per land with the Valley's as hub, sleep needs everyone in every land

docs/WORLDLETS_DESIGN.md

@@ -363,8 +363,10 @@ tunnel goes **down**, inside the cliff, from the clifftop to the shore.
   meat, clay jars) becomes what you carry between them.
 - **Your bases stay** where you built them: each worldlet keeps its own
   save file, so your Valley hut, chests and jars are waiting.
-- **Time:** a worldlet you're not in stands still (as a server does with
-  nobody on), so a base you left doesn't starve or get raided.
+- **Time:** there's one clock for every land (see the decisions below). A
+  worldlet you're not in doesn't run, but catches up on the time when you
+  come back, as after a night's sleep; nothing roams it meanwhile, so a base
+  you left isn't raided.
 
 ### Building it (phases)
 | Phase | Delivers | Done when |
@@ -395,17 +397,45 @@ A server today runs one island. Options:
   bites can make you sick, and bog, mist and the like. Others in the same
   spirit per biome (to design with each worldlet).
 - **Multiplayer: spread out.** Each player goes where they like; the server
-  runs every worldlet someone is in, and the rest stand still. Built in J3,
-  after single-player travel works. What that means for the code:
-  - one server process holds several worldlet scenes, each with its own
-    clock, weather, creatures and save file;
-  - every player belongs to one worldlet at a time, and the server only
-    sends them that worldlet's world, creatures, sounds and chat-free events
-    (chat and the player list stay server-wide);
-  - a crossing moves a player from one worldlet to another (save their
-    place, load or wake the other worldlet, send them its world);
-  - sleep: "everyone in bed" counts the players in that worldlet only;
-  - the Old Stag and other bosses scale with the players in their worldlet.
+  runs every worldlet someone is in. Built in J3, after single-player travel
+  works.
+- **A server per land (Paul, Nov 2026)**, rather than one process holding
+  several worldlets (which would mean making every network module, the
+  saves and the actions handle several worlds at once):
+  - the Valley's server is the **hub**: the address everyone joins. It
+    starts a server for another land (the next UDP port: 24243 the Cove,
+    and so on) when someone first goes there, and stops it a couple of
+    minutes after its last player leaves;
+  - each land server is today's server, with its own worldlet, save file,
+    weather and creatures; it keeps a private link to the hub on the host
+    machine;
+  - characters live in one shared folder. A crossing saves your character
+    first, marks you as on your way, and hands your game the land's port
+    and a one-time pass; your game reconnects there ("On to the Cove...").
+    Nothing can be lost or copied on the way: crash mid-way and you come
+    back where you were going. Joining the hub when your character's in
+    another land sends you straight on there;
+  - chat, the player list (with where each player is) and admin commands
+    go through the hub to every land;
+  - the tunnel belongs to the Valley's server; the Cove's asks the hub
+    whether it's dug through;
+  - from the internet, friends need those extra ports forwarded too (on a
+    home network, nothing to do). The Host page will list them;
+  - the Old Stag and other bosses scale with the players in their land.
+  - Phases: **J3a** the tunnel online, land servers on demand, the
+    crossing and the shared characters; **J3b** chat, the player list and
+    admin across lands; **J3c** the awkward cases (a land server crashing,
+    rejoining mid-crossing, the Host page's ports).
+- **One clock for every land (Paul, Nov 2026).** The day and hour are the
+  same everywhere, so the lands never drift apart:
+  - sleeping until morning needs **everyone, in every land**, in bed (on a
+    server the hub counts them all, and every land skips to morning
+    together);
+  - a land nobody is in doesn't run, but when someone arrives it catches up
+    on the time since anyone was last there, as after a night's sleep:
+    kilns and smelters work, fires burn down, food goes off, trees and
+    berries grow back. (Built for single-player already: `world.catch_up()`.)
+    No creatures roam it meanwhile, so a base you left isn't raided.
 - **Boats: one each, no passengers.** A boat belongs to whoever built it
   (like a bed): only the owner, and their friends under the server's locks
   rule, can sail it, and nobody else can dismantle it. It stays moored where
@@ -439,7 +469,7 @@ One worldlet, a dedicated server on the M5 Pro, never pausing: about
 creatures, weather and pickups around them. So with *spread out*, the worst
 case of 8 players in all 5 worldlets is about five of today's servers in
 one process: roughly 1.4 GB and a little over half a core before players,
-and worldlets with nobody in them stand still and cost next to nothing.
+and worldlets with nobody in them aren't running and cost nothing (each starts its own server when someone goes there).
 Comfortable on the home Mac; a small cloud server (2 GB) would be tight.
 
 ### (Answered) questions