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
+Status: **W0, W1 and W2 built**; the rest is planned. The journey between
-§10.
+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

scripts/world/terrain.gd

@@ -41,6 +41,15 @@ signal ready_built   ## emitted once the mesh + collision exist
 @export var cliff_offset: float = 4.0          ## cliff edge, in rim distance past play_radius
 @export var cliff_drop_width: float = 6.0      ## horizontal run of the drop (smaller = sheerer)
 
+@export_group("Beach")   # (W2: a worldlet's "beach" block; the Valley has none)
+@export var beach_angle_deg: float = 90.0
+@export var beach_half_width_deg: float = 40.0
+@export var beach_fade_deg: float = 20.0
+@export var shore_offset: float = -10.0        ## waterline, in rim distance past play_radius
+@export var beach_slope: float = 0.08          ## metres deeper per metre out
+@export var current_out: float = 20.0          ## the current starts this far past the waterline
+@export var wall_out: float = 34.0             ## and the invisible wall stands here
+
 @export_group("Water & snow")
 @export var water_level: float = -2.6
 @export var lake_center: Vector2 = Vector2(14.0, -46.0)
@@ -132,31 +141,54 @@ func _cliff_d() -> float:
 	return play_radius + cliff_offset
 
 ## 1 on the open-sea side of the rim, 0 where the mountains are, smooth between
-## (the headlands). Depends only on the angle from the centre.
+## (the headlands). Depends only on the angle from the centre. (0 everywhere
+## in a worldlet with no sea cliff.)
 func _sea_w(x: float, z: float) -> float:
+	if not _has_sea:
+		return 0.0
 	var diff := absf(wrapf(atan2(z, x) - deg_to_rad(sea_angle_deg), -PI, PI))
 	return 1.0 - smoothstep(deg_to_rad(sea_half_width_deg), deg_to_rad(sea_half_width_deg + sea_fade_deg), diff)
 
-## Boundary threshold in rim distance: partway up the mountains, or just
+## The same for a beach (W2): 1 where the land runs down into the sea.
-## inside the cliff edge on the sea side.
+func _beach_w(x: float, z: float) -> float:
+	if not _has_beach:
+		return 0.0
+	var diff := absf(wrapf(atan2(z, x) - deg_to_rad(beach_angle_deg), -PI, PI))
+	return 1.0 - smoothstep(deg_to_rad(beach_half_width_deg), deg_to_rad(beach_half_width_deg + beach_fade_deg), diff)
+
+## The waterline of the beach, in rim distance.
+func _shore_d() -> float:
+	return play_radius + shore_offset
+
+## Boundary threshold in rim distance: partway up the mountains, just
+## inside the cliff edge on the sea side, or well out in the water off a
+## beach (where the current turns you back before you reach it).
 func _wall_threshold(x: float, z: float) -> float:
-	return lerpf(_wall_d(), _cliff_d() - 1.0, _sea_w(x, z))
+	var t := lerpf(_wall_d(), _cliff_d() - 1.0, _sea_w(x, z))
+	if _has_beach:
+		t = lerpf(t, _shore_d() + wall_out, _beach_w(x, z))
+	return t
 
 # --- worldlets (docs/WORLDLETS_DESIGN.md, W0) ---------------------------------------
 # A worldlet's terrain is a list of building blocks applied in order
 # (data/worldlets/<id>.json "terrain"). Each block takes the ground so far and
 # returns it changed; "hills" starts it. A worldlet can only combine these.
 
-const BLOCKS := ["hills", "rim", "sea_cliff", "lake", "ocean_edge"]
+const BLOCKS := ["hills", "rim", "sea_cliff", "beach", "lake", "ocean_edge"]
 var worldlet_id := "valley"
 var worldlet: Dictionary = {}           ## the definition, as loaded
 var _blocks: Array = []                 ## its terrain blocks, in order
+var lakes: Array = []                   ## every "lake" block's {center: Vector2, radius} (W2: several)
+var _has_sea := true                    ## a sea cliff (the Valley's)
+var _has_beach := false                 ## a beach (W2)
 var _valley := 0.0                      ## the hills before anything else (the sea cliff eases from it)
 var _detail_k := 1.4
 
 ## The definition of worldlet `id` (data/worldlets/<id>.json), or {} if none.
 static func load_worldlet(id: String) -> Dictionary:
 	var p := "res://data/worldlets/%s.json" % id
+	if not FileAccess.file_exists(p):
+		p = "res://tests/worldlets/%s.json" % id   # (test-only worldlets: never listed or offered)
 	if not FileAccess.file_exists(p):
 		return {}
 	var d: Variant = JSON.parse_string(FileAccess.get_file_as_string(p))
@@ -198,6 +230,9 @@ func use_worldlet(id: String) -> String:
 	size = int(d.get("size", size))
 	resolution = int(d.get("resolution", resolution))
 	_blocks = d.get("terrain", [])
+	lakes = []
+	_has_sea = _has_block("sea_cliff")
+	_has_beach = _has_block("beach")
 	for b in _blocks:
 		match String(b.type):
 			"hills":
@@ -217,11 +252,30 @@ func use_worldlet(id: String) -> String:
 				cliff_top = float(b.get("cliff_top", cliff_top))
 				cliff_offset = float(b.get("cliff_offset", cliff_offset))
 				cliff_drop_width = float(b.get("drop_width", cliff_drop_width))
+			"beach":
+				beach_angle_deg = float(b.get("angle_deg", beach_angle_deg))
+				beach_half_width_deg = float(b.get("half_width_deg", beach_half_width_deg))
+				beach_fade_deg = float(b.get("fade_deg", beach_fade_deg))
+				shore_offset = float(b.get("shore_offset", shore_offset))
+				beach_slope = float(b.get("slope", beach_slope))
+				current_out = float(b.get("current_out", current_out))
+				wall_out = float(b.get("wall_out", wall_out))
 			"lake":
+				# Every lake and pond shares one surface (water_level): the
+				# first lake sets it, and is "the lake" to the older code
+				# (lake_center/lake_radius: ice, its fish, the tutorial).
 				var c: Array = b.get("center", [lake_center.x, lake_center.y])
-				lake_center = Vector2(float(c[0]), float(c[1]))
+				var at := Vector2(float(c[0]), float(c[1]))
-				lake_radius = float(b.get("radius", lake_radius))
+				var r := float(b.get("radius", lake_radius))
-				water_level = float(b.get("water_level", water_level))
+				b["_c"] = at
+				b["_r"] = r
+				if lakes.is_empty():
+					lake_center = at
+					lake_radius = r
+					water_level = float(b.get("water_level", water_level))
+				lakes.append({"center": at, "radius": r})
+	if _has_beach:
+		sea_level = water_level   # (a beach runs into the sea: one surface)
 	snow_height = float(d.get("climate", {}).get("snowline", snow_height))
 	return ""
 
@@ -244,8 +298,10 @@ func _height_fn(x: float, z: float) -> float:
 				land = _blk_rim(x, z, land)
 			"sea_cliff":
 				land = _blk_sea_cliff(x, z, land)
+			"beach":
+				land = _blk_beach(x, z, land)
 			"lake":
-				land = _blk_lake(x, z, land)
+				land = _blk_lake(x, z, land, b._c, b._r)
 			"ocean_edge":
 				land = _blk_ocean_edge(x, z, land)
 	return land
@@ -293,10 +349,27 @@ func _blk_sea_cliff(x: float, z: float, land: float) -> float:
 	return land
 
 ## A lake basin: the ground blends down to a bed below the waterline.
-func _blk_lake(x: float, z: float, land: float) -> float:
+func _blk_lake(x: float, z: float, land: float, at: Vector2, r: float) -> float:
-	var ld := Vector2(x - lake_center.x, z - lake_center.y).length()
+	var ld := Vector2(x - at.x, z - at.y).length()
 	ld += _detail.get_noise_2d(x * 0.5, z * 0.5) * 5.0
-	return lerpf(land, water_level - 3.2, smoothstep(lake_radius, lake_radius * 0.35, ld))
+	return lerpf(land, water_level - 3.2, smoothstep(r, r * 0.35, ld))
+
+## A beach (W2): on its side of the rim the land eases down to a sandy
+## waterline, then shelves gently into the sea (beach_slope deeper per
+## metre), so you can wade, then swim, until the current turns you back.
+func _blk_beach(x: float, z: float, land: float) -> float:
+	var bw := _beach_w(x, z)
+	if bw <= 0.0:
+		return land
+	var d := _rim_d(x, z)
+	var shore := _shore_d()
+	var profile: float
+	if d < shore:
+		profile = water_level + (shore - d) * 0.12 + _detail.get_noise_2d(x * 0.5, z * 0.5) * 0.3
+	else:
+		profile = maxf(water_level - (d - shore) * beach_slope, water_level - 14.0) + _detail.get_noise_2d(x, z) * 0.25
+	var coast := lerpf(_valley, profile, smoothstep(shore - 50.0, shore - 8.0, d))
+	return lerpf(land, coast, bw)
 
 ## Ocean all round the chunk edge, so the world is an island and the edge of
 ## the mesh is always hidden under deep water.
@@ -496,7 +569,8 @@ func _build_water() -> void:
 	arrays[Mesh.ARRAY_INDEX] = idx
 	var disc := ArrayMesh.new()
 	disc.add_surface_from_arrays(Mesh.PRIMITIVE_TRIANGLES, arrays)
-	_add_water("Water", disc, water_level, {})
+	if absf(sea_level - water_level) > 0.05:   # (by a beach the sea is the same surface: no second sheet)
+		_add_water("Water", disc, water_level, {})
 
 	var ocean := PlaneMesh.new()
 	ocean.size = Vector2(8000.0, 8000.0)
@@ -537,6 +611,26 @@ func sea_weight(x: float, z: float) -> float:
 	_ensure_noise()
 	return _sea_w(x, z)
 
+## How strongly (x, z) lies on the beach side of the rim (0..1; W2).
+func beach_weight(x: float, z: float) -> float:
+	_ensure_noise()
+	return _beach_w(x, z)
+
+## Off a beach, the current that turns swimmers back before the wall: 0
+## (none) to 1 (full strength, just inside the wall). Always 0 elsewhere.
+func current_at(x: float, z: float) -> float:
+	_ensure_noise()
+	if _beach_w(x, z) < 0.5:
+		return 0.0
+	var from := _shore_d() + current_out
+	return smoothstep(from, maxf(_wall_threshold(x, z) - 3.0, from + 1.0), _rim_d(x, z))
+
+## A point out in the bay off the beach, `past_shore` metres beyond the waterline.
+func shore_point(past_shore: float) -> Vector2:
+	_ensure_noise()
+	var dir := Vector2(cos(deg_to_rad(beach_angle_deg)), sin(deg_to_rad(beach_angle_deg)))
+	return dir * (_shore_d() + past_shore - _rim_offset(dir.x, dir.y))
+
 ## Point on the coast along `angle_deg` (atan2(z, x) convention), at rim
 ## distance `past_edge` beyond the cliff edge (negative = inland of it).
 func coast_point(angle_deg: float, past_edge: float) -> Vector2:

scripts/world/world.gd

@@ -811,7 +811,8 @@ func _respawn() -> void:
 	player.rotation = Vector3(0.0, _spawn_yaw, 0.0)
 	player.get_node("Camera3D").rotation.x = 0.0
 
-func _physics_process(_delta: float) -> void:
+func _physics_process(delta: float) -> void:
+	_current(delta)
 	var p := player.global_position
 	var half: float = terrain.size * 0.5
 	if p.y < terrain.min_height - 30.0 or absf(p.x) > half or absf(p.z) > half \
@@ -819,6 +820,25 @@ func _physics_process(_delta: float) -> void:
 		push_warning("[world] player left the map at %s; respawning" % p)
 		_respawn()
 
+## Off a beach (W2), a current carries anyone swimming too far out back
+## towards the shore: the sea's version of the invisible wall. It's faster
+## than you can swim, so you can't push through it, and it says so once.
+const CURRENT_SPEED := 4.5
+var _in_current := false
+
+func _current(delta: float) -> void:
+	var p := player.global_position
+	var c: float = terrain.current_at(p.x, p.z) if p.y < terrain.sea_level else 0.0
+	if c <= 0.0:
+		_in_current = false
+		return
+	var back := -Vector3(p.x, 0.0, p.z).normalized()
+	player.global_position += back * CURRENT_SPEED * c * delta
+	if not _in_current and c > 0.2:
+		_in_current = true
+		if hud != null:
+			hud.toast("A strong current pulls you back towards the shore")
+
 # --- building ---------------------------------------------------------------
 
 ## Whether a piece can go at `xf`: inside the valley, on dry fairly flat
@@ -887,11 +907,14 @@ func _update_grass_cuts() -> void:
 ## fishing (and later swimming, boats) work on any world that answers it.
 func water_at(x: float, z: float) -> Dictionary:
 	var ground: float = terrain.sample_height(x, z)
+	var beach: bool = terrain.beach_weight(x, z) > 0.5
 	if terrain.inside_boundary(x, z, -2.0) and ground < terrain.water_level:
+		if beach and not _in_lake(x, z):
+			return {"type": "sea", "surface": terrain.sea_level, "depth": terrain.sea_level - ground}
 		if hazards != null and hazards.iced(x, z):
 			return {}   # (frozen over in a hard winter: cast further out)
 		return {"type": "lake", "surface": terrain.water_level, "depth": terrain.water_level - ground}
-	if terrain.sea_weight(x, z) > 0.5 and ground < terrain.sea_level:
+	if (beach or terrain.sea_weight(x, z) > 0.5) and ground < terrain.sea_level:
 		return {"type": "sea", "surface": terrain.sea_level, "depth": terrain.sea_level - ground}
 	return {}
 
@@ -916,12 +939,22 @@ func water_bodies() -> Array:
 		match String(b.type):
 			"lake":
 				out.append({"type": "lake", "surface": terrain.water_level,
-					"center": terrain.lake_center, "radius": terrain.lake_radius})
+					"center": b._c, "radius": b._r})
 			"sea_cliff":
 				out.append({"type": "sea", "surface": terrain.sea_level,
 					"center": terrain.coast_point(terrain.sea_angle_deg, 20.0), "radius": 0.0})
+			"beach":
+				out.append({"type": "sea", "surface": terrain.sea_level,
+					"center": terrain.shore_point(12.0), "radius": 0.0})
 	return out
 
+## Whether (x, z) is in one of the lakes or ponds (not the sea off a beach).
+func _in_lake(x: float, z: float) -> bool:
+	for l in terrain.lakes:
+		if Vector2(x - l.center.x, z - l.center.y).length() < float(l.radius) * 1.3:
+			return true
+	return false
+
 ## Its climate: {"snowline": m, ...} (more as worldlets differ).
 func climate() -> Dictionary:
 	var c: Dictionary = terrain.worldlet.get("climate", {}).duplicate()

tests/run_all.sh

@@ -9,7 +9,7 @@ if [ ! -f .godot/global_script_class_cache.cfg ]; then
 	echo "Importing the project first (fresh copy)..."
 	godot --headless --path . --import >/dev/null 2>&1
 fi
-for t in test_survival_core test_survival_stats test_save_load test_weather_building test_creatures_combat test_wolves test_alpha test_bear test_thieves test_barrow test_boss test_den_sites test_fishing_diet test_food test_hazards test_iron test_stone test_net_lobby test_net_world test_net_shared test_net_life test_net_boss test_net_rules test_host test_tutorial test_tutorial_full test_hints test_updates test_audio test_items_more test_worldlets test_worldlet_pick test_terrain_edges test_boundary; do
+for t in test_survival_core test_survival_stats test_save_load test_weather_building test_creatures_combat test_wolves test_alpha test_bear test_thieves test_barrow test_boss test_den_sites test_fishing_diet test_food test_hazards test_iron test_stone test_net_lobby test_net_world test_net_shared test_net_life test_net_boss test_net_rules test_host test_tutorial test_tutorial_full test_hints test_updates test_audio test_items_more test_worldlets test_worldlet_pick test_water_bodies test_terrain_edges test_boundary; do
 	extra=""
 	[ "$t" = "test_boundary" ] && extra="--fixed-fps 30"
 	# A suite that waits on a world that failed to load would hang forever,

tests/test_boundary.gd

@@ -4,34 +4,63 @@ extends SceneTree
 ## the invisible wall, falls off the map, or ends up stuck below the waterline
 ## (in a pit near the edge).
 ##
+## Then the same on a worldlet with a beach (W2, tests/worldlets/testbay.json):
+## off the beach you swim out into the sea, and the current must turn you back
+## before the wall (being afloat in the open sea there is fine).
+##
 ## Run: godot --headless --path . --fixed-fps 30 --script res://tests/test_boundary.gd
 
 const DIRECTIONS := 24
+const BAY_DIRECTIONS := 8         # (spread over the beach and its headlands)
 const SECONDS_PER_TRY := 25.0
 
+var _failures := 0
+var _tries := 0
+
 func _initialize() -> void:
+	_run.call_deferred()
+
+func _run() -> void:
+	var S: Node = root.get_node("Saves")
+	S.root_dir = "user://test_boundary_worlds"
+	for w in S.list_worlds():
+		S.delete_world(w.id)
+	print("the Valley")
+	await _escape_all(DIRECTIONS, -1.0)
+	print("a beach (testbay)")
+	S.current_id = S.create_world("Bay", 1337, {"worldlet": "testbay"})
+	await _escape_all(BAY_DIRECTIONS, 90.0)
+	for w in S.list_worlds():
+		S.delete_world(w.id)
+	DirAccess.remove_absolute(S.root_dir)
+	print("RESULT: %s (%d/%d directions held)" % ["PASS" if _failures == 0 else "FAIL", _tries - _failures, _tries])
+	quit(1 if _failures > 0 else 0)
+
+## Walks out in `count` directions: all round, or (beach_deg >= 0) across the
+## beach's arc and a little past it either side.
+func _escape_all(count: int, beach_deg: float) -> void:
 	var world: Node3D = load("res://scenes/world.tscn").instantiate()
 	root.add_child(world)
-	_run.call_deferred(world)
-
-func _run(world: Node3D) -> void:
 	for _i in range(10):
 		await physics_frame
 	var terrain: Node3D = world.get_node("Terrain")
 	var player: CharacterBody3D = world.get_node("Player")
-	var failures := 0
 	var tick := 1.0 / Engine.physics_ticks_per_second
-	for i in range(DIRECTIONS):
+	var pulled := 0
-		var ang := TAU * i / DIRECTIONS
+	for i in range(count):
+		var ang := TAU * i / count
+		if beach_deg >= 0.0:
+			ang = deg_to_rad(beach_deg + lerpf(-65.0, 65.0, float(i) / (count - 1)))
 		var out := Vector3(cos(ang), 0.0, sin(ang))
 		var start: Vector3 = out * (terrain.play_radius - 12.0)
-		start.y = terrain.sample_height(start.x, start.z) + 1.0
+		start.y = maxf(terrain.sample_height(start.x, start.z), terrain.water_level) + 1.0
 		player.global_position = start
 		player.velocity = Vector3.ZERO
 		player.rotation = Vector3(0.0, atan2(-out.x, -out.z), 0.0)
 		Input.action_press("move_forward")
 		var escaped := false
 		var max_d := 0.0
+		var in_current := false
 		var frames := int(SECONDS_PER_TRY / tick)
 		for f in range(frames):
 			if f % 12 == 0:
@@ -41,17 +70,28 @@ func _run(world: Node3D) -> void:
 			await physics_frame
 			var p := player.global_position
 			max_d = maxf(max_d, Vector2(p.x, p.z).length())
+			in_current = in_current or terrain.current_at(p.x, p.z) > 0.2
 			if not terrain.inside_boundary(p.x, p.z, -1.5) or p.y < terrain.min_height - 5.0:
 				escaped = true
 				break
 		Input.action_release("move_forward")
 		Input.action_release("jump")
 		var p := player.global_position
-		if not escaped and p.y < terrain.water_level - 0.5:
+		var at_sea: bool = world.water_at(p.x, p.z).get("type", "") == "sea"
+		if not escaped and p.y < terrain.water_level - 0.5 and not at_sea:
 			escaped = true   # stuck in a pit below the waterline
-		print("dir %2d (%3d deg): %s  max radius %.1f  final (%.1f, %.1f, %.1f)" % [
+		if in_current:
-			i, int(rad_to_deg(ang)), "FAILED" if escaped else "held", max_d, p.x, p.y, p.z])
+			pulled += 1
+		print("dir %2d (%3d deg): %s  max radius %.1f  final (%.1f, %.1f, %.1f)%s" % [
+			i, int(rad_to_deg(ang)), "FAILED" if escaped else "held", max_d, p.x, p.y, p.z,
+			"  (the current turned them back)" if in_current else ""])
+		_tries += 1
 		if escaped:
-			failures += 1
+			_failures += 1
-	print("RESULT: %s (%d/%d directions held)" % ["PASS" if failures == 0 else "FAIL", DIRECTIONS - failures, DIRECTIONS])
+	if beach_deg >= 0.0 and pulled == 0:
-	quit(1 if failures > 0 else 0)
+		print("FAILED: nobody swam far enough out to meet the current")
+		_failures += 1
+		_tries += 1
+	world.queue_free()
+	for _i in range(3):
+		await process_frame

tests/test_terrain_edges.gd

@@ -19,18 +19,25 @@ const SEEDS := [1337, 1, 42, 777, 4242, 9001, 31337, 123456]
 func _initialize() -> void:
 	_all.call_deferred()
 
+## Each worldlet's edges (W2): the Valley, and a test worldlet with two
+## ponds and a beach (tests/worldlets/testbay.json).
+const WORLDLETS := ["valley", "testbay"]
+
 func _all() -> void:
 	var failed := 0
-	for s in SEEDS:
+	for w in WORLDLETS:
-		var terrain: Node3D = load("res://scripts/world/terrain.gd").new()
+		for s in SEEDS:
-		terrain.noise_seed = s
+			var terrain: Node3D = load("res://scripts/world/terrain.gd").new()
-		root.add_child(terrain)   # builds in _ready
+			terrain.noise_seed = s
-		var bad := _check(terrain)
+			terrain.worldlet_id = w
-		print("seed %6d: %s" % [s, "ok" if bad == 0 else "%d bad samples" % bad])
+			root.add_child(terrain)   # builds in _ready
-		if bad > 0:
+			var bad := _check(terrain)
-			failed += 1
+			print("%-8s seed %6d: %s" % [w, s, "ok" if bad == 0 and terrain.worldlet_id == w else "%d bad samples" % bad])
-		terrain.free()
+			if bad > 0 or terrain.worldlet_id != w:
-	print("RESULT: %s (%d/%d seeds clean)" % ["PASS" if failed == 0 else "FAIL", SEEDS.size() - failed, SEEDS.size()])
+				failed += 1
+			terrain.free()
+	var n := WORLDLETS.size() * SEEDS.size()
+	print("RESULT: %s (%d/%d seeds clean)" % ["PASS" if failed == 0 else "FAIL", n - failed, n])
 	quit(1 if failed > 0 else 0)
 
 func _check(terrain: Node3D) -> int:
@@ -42,7 +49,10 @@ func _check(terrain: Node3D) -> int:
 	while x < half:
 		var z := -half
 		while z < half:
-			if terrain.inside_boundary(x, z, 0.0) and not terrain.inside_boundary(x, z, BAND):
+			# (Off a beach the edge is open sea, and the current keeps you
+			# from the wall: tests/test_boundary.gd swims out there.)
+			if terrain.inside_boundary(x, z, 0.0) and not terrain.inside_boundary(x, z, BAND) \
+					and terrain.beach_weight(x, z) <= 0.5:
 				var h: float = terrain.sample_height(x, z)
 				# Hazard 1: a pit too deep to wade out of near the edge.
 				var too_deep: bool = h < terrain.water_level - MAX_EDGE_DEPTH

tests/test_water_bodies.gd

@@ -0,0 +1,123 @@
+extends SceneTree
+## W2 (docs/WORLDLETS_DESIGN.md): several bodies of water in one world, and a
+## beach. On a test worldlet with two ponds and a beach
+## (tests/worldlets/testbay.json): the world lists both ponds and the sea,
+## water_at() knows which is which, the beach shelves gently into the sea,
+## the sea there is one surface (no second water sheet), and a swimmer out
+## past the shallows is carried back by the current. The Valley has no
+## current anywhere.
+## Run: godot --headless --path . --script res://tests/test_water_bodies.gd
+
+var _fails := 0
+var _finished := false
+
+func check(cond: bool, what: String) -> void:
+	print(("  ok   " if cond else "  FAIL ") + what)
+	if not cond:
+		_fails += 1
+
+func _initialize() -> void:
+	_run.call_deferred()
+
+func _run() -> void:
+	var S: Node = root.get_node("Saves")
+	S.root_dir = "user://test_water_worlds"
+	for w in S.list_worlds():
+		S.delete_world(w.id)
+	await _body(S)
+	check(_finished, "test ran to the end (no script errors)")
+	for w in S.list_worlds():
+		S.delete_world(w.id)
+	DirAccess.remove_absolute(S.root_dir)
+	print("RESULT: %s (%d failures)" % ["PASS" if _fails == 0 else "FAIL", _fails])
+	quit(1 if _fails > 0 else 0)
+
+func _body(S: Node) -> void:
+	var T: Script = load("res://scripts/world/terrain.gd")
+	check(not T.worldlets().any(func(w): return w.id == "testbay"), "the test worldlet is never listed (nor offered)")
+	print("the Valley: no current")
+	var v: Node3D = T.new()
+	root.add_child(v)
+	await process_frame
+	var any := false
+	for i in range(72):
+		var a := TAU * i / 72.0
+		for r in [60.0, 100.0, 110.0, 120.0]:
+			any = any or v.current_at(cos(a) * r, sin(a) * r) > 0.0
+	check(not any, "nowhere in the Valley has a current")
+	check(v.lakes.size() == 1 and v.lakes[0].center == Vector2(14, -46), "and its one lake is the old one")
+	v.free()
+
+	print("two ponds and a beach")
+	S.current_id = S.create_world("Bay", 1337, {"worldlet": "testbay"})
+	var world: Node3D = load("res://scenes/world.tscn").instantiate()
+	root.add_child(world)
+	for _i in range(8):
+		await physics_frame
+	var t: Node3D = world.terrain
+	check(world.worldlet_id() == "testbay", "the world is the test bay")
+	var bodies: Array = world.water_bodies()
+	var ponds: Array = bodies.filter(func(b): return b.type == "lake")
+	var seas: Array = bodies.filter(func(b): return b.type == "sea")
+	check(ponds.size() == 2 and seas.size() == 1, "its water: two ponds and the sea (%s)" % [bodies.map(func(b): return b.type)])
+	for p in ponds:
+		var c: Vector2 = p.center
+		var w: Dictionary = world.water_at(c.x, c.y)
+		check(w.get("type", "") == "lake" and float(w.get("depth", 0.0)) > 2.0,
+			"the pond at (%.0f, %.0f) is water, %.1f m deep" % [c.x, c.y, float(w.get("depth", 0.0))])
+	var bay: Vector2 = seas[0].center
+	var sw: Dictionary = world.water_at(bay.x, bay.y)
+	check(sw.get("type", "") == "sea", "out in the bay is the sea (%s)" % [sw])
+	check(absf(t.sea_level - t.water_level) < 0.01, "the sea off a beach is at the ponds' level (%.1f)" % t.sea_level)
+	check(t.get_node_or_null("Water") == null and t.get_node_or_null("Ocean") != null, "one water surface: the ocean, no second sheet")
+
+	print("the beach")
+	# Walking straight out from the middle of the beach: dry land, the
+	# waterline, then gently deeper (no cliff), then the current, then the wall.
+	var dir := Vector2(cos(deg_to_rad(t.beach_angle_deg)), sin(deg_to_rad(t.beach_angle_deg)))
+	var shore := -1.0
+	var current := -1.0
+	var wall := -1.0
+	var steepest := 0.0
+	var prev: float = t.sample_height(dir.x * 40.0, dir.y * 40.0)
+	var r := 41.0
+	while r < 150.0:
+		var q := dir * r
+		var h: float = t.sample_height(q.x, q.y)
+		if r > 60.0:
+			steepest = maxf(steepest, absf(h - prev))
+		prev = h
+		if shore < 0.0 and h < t.water_level:
+			shore = r
+		if current < 0.0 and t.current_at(q.x, q.y) > 0.0:
+			current = r
+		if wall < 0.0 and not t.inside_boundary(q.x, q.y):
+			wall = r
+		r += 1.0
+	check(shore > 0.0 and current > shore and wall > current, "dry land, the waterline at %.0f m, the current from %.0f m, the wall at %.0f m" % [shore, current, wall])
+	check(steepest < 0.5, "a gentle shelf, never a drop (steepest %.2f m per metre)" % steepest)
+	var depth_at_current: float = t.water_level - t.sample_height(dir.x * current, dir.y * current)
+	check(depth_at_current > 1.3, "the current starts where you're swimming, not wading (%.1f m deep)" % depth_at_current)
+
+	print("the current")
+	var player: CharacterBody3D = world.player
+	player.set_physics_process(false)   # (no swimming: just drift)
+	var start := dir * (wall - 4.0)
+	player.global_position = Vector3(start.x, t.water_level - 1.3, start.y)
+	var d0 := start.length()
+	for _i in range(60):
+		await physics_frame
+	var p := player.global_position
+	var d1 := Vector2(p.x, p.z).length()
+	check(d1 < d0 - 1.5, "a swimmer by the wall is carried back towards the shore (%.1f m in a second)" % (d0 - d1))
+	check(world._in_current, "(and told so)")
+	var near := dir * (shore + 2.0)
+	player.global_position = Vector3(near.x, t.water_level - 0.5, near.y)
+	for _i in range(30):
+		await physics_frame
+	p = player.global_position
+	check(absf(Vector2(p.x, p.z).length() - (shore + 2.0)) < 0.01, "but nothing pulls at you in the shallows")
+	check(t.find_spawn(Vector2.ZERO).y > t.water_level + 1.0, "the start is on dry land")
+	world.queue_free()
+	await process_frame
+	_finished = true

tests/test_water_bodies.gd.uid

@@ -0,0 +1 @@
+uid://da1vwsptqh68b

tests/worldlets/testbay.json

@@ -0,0 +1,17 @@
+{
+  "_doc": "Test-only worldlet (W2): the Valley's hills and rim, but a beach instead of the sea cliff and two ponds instead of the lake. Found by terrain.gd's load_worldlet() after data/worldlets/, never listed or offered. Used by tests/test_water_bodies.gd, test_terrain_edges.gd and test_boundary.gd.",
+  "id": "testbay",
+  "name": "Test Bay",
+  "description": "Hills, two ponds and a beach (tests only).",
+  "size": 320,
+  "resolution": 256,
+  "terrain": [
+    {"type": "hills", "height_scale": 7.0, "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": "beach", "angle_deg": 90.0, "half_width_deg": 40.0, "fade_deg": 20.0, "shore_offset": -10.0, "slope": 0.08, "current_out": 20.0, "wall_out": 34.0},
+    {"type": "lake", "center": [-40.0, -35.0], "radius": 14.0, "water_level": -2.6},
+    {"type": "lake", "center": [35.0, -45.0], "radius": 11.0},
+    {"type": "ocean_edge"}
+  ],
+  "climate": {"snowline": 40.0}
+}