W0: terrain from worldlet building blocks (Valley in data/worldlets, identical heights), WorldInfo API, worldlet in saves and servers; the cliff tunnel plan

data/worldlets/valley.json

@@ -0,0 +1,17 @@
+{
+  "_doc": "A worldlet (docs/WORLDLETS_DESIGN.md): its size, and its terrain as building blocks applied in order (scripts/world/terrain.gd: hills, rim, sea_cliff, lake, ocean_edge). The numbers here are the Valley exactly as it was hand-coded: tests/test_worldlets.gd checks it still makes the same height grid.",
+  "id": "valley",
+  "name": "Valley",
+  "description": "A sheltered valley ringed by mountains, with a lake in the middle and sea cliffs on one side.",
+  "size": 320,
+  "resolution": 256,
+  "terrain": [
+    {"type": "hills", "height_scale": 9.0, "detail": 1.4},
+    {"type": "rim", "play_radius": 100.0, "rim_width": 30.0, "mountain_height": 58.0, "rim_warp": 16.0, "wall_frac": 0.45},
+    {"type": "sea_cliff", "angle_deg": -75.0, "half_width_deg": 38.0, "fade_deg": 22.0, "sea_level": -24.0, "cliff_top": 0.5, "cliff_offset": 4.0, "drop_width": 6.0},
+    {"type": "lake", "center": [14.0, -46.0], "radius": 24.0, "water_level": -2.6},
+    {"type": "ocean_edge"}
+  ],
+  "climate": {"snowline": 40.0},
+  "next": [{"to": "cove", "by": "tunnel", "where": "sea_cliff"}]
+}