diff --git a/map_gen/shared/builders.lua b/map_gen/shared/builders.lua
index 9b51a3e1..13259780 100644
--- a/map_gen/shared/builders.lua
+++ b/map_gen/shared/builders.lua
@@ -158,7 +158,8 @@ function Builders.rectangular_spiral(x_size, optional_y_size)
     end
 end
 
-function Builders.circular_spiral(out_thickness, total_thickness)
+function Builders.circular_spiral(in_thickness, total_thickness)
+    local out_thickness = total_thickness - in_thickness
     local half_total_thickness = total_thickness * 0.5
     return function(x, y)
         local d = math.sqrt(x * x + y * y)
@@ -170,6 +171,25 @@ function Builders.circular_spiral(out_thickness, total_thickness)
     end
 end
 
+function Builders.circular_spiral_grow(in_thickness, total_thickness, grow_factor)
+    local out_thickness = total_thickness - in_thickness
+    local half_total_thickness = total_thickness * 0.5
+    local inv_grow_factor = 1 / grow_factor
+    return function(x, y)
+        local d = math.sqrt(x * x + y * y)
+
+        local factor = (d * inv_grow_factor) + 1
+        local total_thickness2 = total_thickness * factor
+        local out_thickness2 = out_thickness * factor
+        local half_total_thickness2 = half_total_thickness * factor
+
+        local angle = 1 + inv_pi * math.atan2(x, y)
+        local offset = d + (angle * half_total_thickness2)
+
+        return offset % total_thickness2 >= out_thickness2
+    end
+end
+
 function Builders.circular_spiral_n_threads(in_thickness, total_thickness, n_threads)
     local out_thickness = total_thickness - in_thickness
     local half_total_thickness = total_thickness * 0.5 * n_threads
@@ -183,6 +203,25 @@ function Builders.circular_spiral_n_threads(in_thickness, total_thickness, n_thr
     end
 end
 
+function Builders.circular_spiral_grow_n_threads(in_thickness, total_thickness, grow_factor, n_threads)
+    local out_thickness = total_thickness - in_thickness
+    local half_total_thickness = total_thickness * 0.5 * n_threads
+    local inv_grow_factor = 1 / grow_factor
+    return function(x, y)
+        local d = math.sqrt(x * x + y * y)
+
+        local factor = (d * inv_grow_factor) + 1
+        local total_thickness2 = total_thickness * factor
+        local out_thickness2 = out_thickness * factor
+        local half_total_thickness2 = half_total_thickness * factor
+
+        local angle = 1 + inv_pi * math.atan2(x, y)
+        local offset = d + (angle * half_total_thickness2)
+
+        return offset % total_thickness2 >= out_thickness2
+    end
+end
+
 local tile_map = {
     [1] = false,
     [2] = true,