fix: improve crab spawning and net targeting

tests/gathering_marker_surface_validation.gd

@@ -22,13 +22,36 @@ func _run() -> void:
 
 	var wall := _make_surface(
 		Vector3(2.0, 2.0, 0.1),
-		Vector3(0.0, 0.9, -1.5),
+		Vector3(0.0, 0.9, -1.1),
 	)
 	root.add_child(wall)
 	await physics_frame
 	controller.call("_update_marker_target")
 	var marker := controller.get("_marker") as MeshInstance3D
 	assert(marker != null)
+	var disc := marker.mesh as CylinderMesh
+	assert(disc != null)
+	assert(is_equal_approx(disc.top_radius, controller.marker_radius))
+	assert(is_equal_approx(disc.bottom_radius, controller.marker_radius))
+	var invalid_material := controller.get(
+		"_marker_invalid_material"
+	) as StandardMaterial3D
+	var valid_material := controller.get(
+		"_marker_valid_material"
+	) as StandardMaterial3D
+	assert(invalid_material != null)
+	assert(valid_material != null)
+	assert(invalid_material.albedo_color == Color.WHITE)
+	assert(is_equal_approx(invalid_material.albedo_color.a, 1.0))
+	assert(is_equal_approx(valid_material.albedo_color.a, 1.0))
+	assert(
+		invalid_material.shading_mode
+		== BaseMaterial3D.SHADING_MODE_UNSHADED
+	)
+	assert(
+		valid_material.shading_mode
+		== BaseMaterial3D.SHADING_MODE_UNSHADED
+	)
 	assert(bool(controller.get("_marker_has_surface")))
 	assert(marker.global_basis.y.dot(Vector3.BACK) > 0.99)
 
@@ -44,6 +67,16 @@ func _run() -> void:
 	assert(bool(controller.get("_marker_has_surface")))
 	assert(marker.global_basis.y.dot(Vector3.UP) > 0.99)
 	assert(is_equal_approx(absf(marker.global_basis.determinant()), 1.0))
+	var horizontal_marker_offset := Vector2(
+		marker.global_position.x - player.global_position.x,
+		marker.global_position.z - player.global_position.z,
+	).length()
+	assert(
+		is_equal_approx(
+			horizontal_marker_offset,
+			controller.marker_distance,
+		)
+	)
 
 	floor.queue_free()
 	controller.queue_free()