W2: several lakes per worldlet, a beach block shelving into the sea with a current that turns swimmers back; testbay test worldlet through the water, edge and boundary suites; the two ways to play (journey, one land) recorded

docs/WORLDLETS_DESIGN.md

@@ -1,7 +1,30 @@
 # Worldlets design
 
-Status: **W0 built**; the rest is planned. The journey between worldlets is
-§10.
+Status: **W0, W1 and W2 built**; the rest is planned. The journey between
+worldlets is §10, and the two ways to play (the journey, or one land) are in
+its decisions.
+
+*As built in W2:*
+- `lake` blocks can repeat: every lake and pond is its own body
+  (`terrain.lakes`, `world.water_bodies()`), all at one surface
+  (`water_level`, set by the first). The first is still "the lake" to the
+  older code (ice, its fish, the tutorial).
+- A `beach` block (angle, width, `shore_offset`, `slope`, `current_out`,
+  `wall_out`): the land eases to a waterline and shelves gently into the
+  sea, which is then the same surface as the ponds (one ocean sheet, no
+  inland disc). The invisible wall stands well out in the water, and before
+  it a current (`terrain.current_at()`, `world._current()`) carries
+  swimmers back faster than they can swim, with a toast.
+- `water_at()` tells the sea off a beach from a pond.
+- Test-only worldlets live in `tests/worldlets/` (never listed or offered).
+  `testbay.json` (two ponds and a beach) runs through
+  `test_water_bodies`, `test_terrain_edges` (8 seeds) and `test_boundary`
+  (swimming out across the beach).
+
+*As built in W1:* a "Where" picker on the New World and Host Game pages
+(worldlets with `"start": true`; only the Valley, so it's greyed out), the
+worldlet in the Load list, and a hosted island keeps its worldlet like its
+seed.
 
 *As built in W0:*
 - `data/worldlets/valley.json`: the Valley as data, its terrain as five
@@ -336,6 +359,22 @@ A server today runs one island. Options:
 - **The other crossings are shared:** a dug tunnel, a fixed climbing rope
   and a dug burrow are changes to the world, there for everyone once one
   player has made them (like a door or a bridge).
+- **Two ways to play (Paul, Nov 2026).**
+  - **The journey** (the standard game), single-player and multiplayer
+    alike: every new world starts in the Valley and the worldlets come in
+    their fixed order (Valley, Cove, Highlands, Marsh, Ember). Each
+    worldlet's shape is set by its definition; the seed only changes the
+    detail (hills, trees, where the den is), so the journey is the same
+    adventure for everyone.
+  - **One land** (a hosting choice): no journey, no crossings, the server
+    is locked to one worldlet, and the host picks which, from all of them.
+    Co-op or PvP as now (the rules preset). In code: a `mode` in
+    `server.json` ("journey" / "one_land"); in one-land mode the Host
+    page's "Where" lists every worldlet rather than only the starts, and
+    the crossings (`world.crossings()`) answer none, so a tunnel seam
+    can't be dug. Kept, like the seed and the worldlet, once the island
+    exists. Worth building once the Cove exists (until then there's only
+    the Valley to pick).
 
 ### Server cost, measured (0.3.1)
 One worldlet, a dedicated server on the M5 Pro, never pausing: about