diff --git a/src/__private__/__to2d.scad b/src/__private__/__to2d.scad
new file mode 100644
index 00000000..865cfcda
--- /dev/null
+++ b/src/__private__/__to2d.scad
@@ -0,0 +1 @@
+function __to2d(p) = [p[0], p[1]];
\ No newline at end of file
diff --git a/src/__private__/__to3d.scad b/src/__private__/__to3d.scad
new file mode 100644
index 00000000..af3d63aa
--- /dev/null
+++ b/src/__private__/__to3d.scad
@@ -0,0 +1 @@
+function __to3d(p) = [p[0], p[1], 0];
\ No newline at end of file
diff --git a/src/cross_sections.scad b/src/cross_sections.scad
index 964ba6e3..e6d5edbc 100644
--- a/src/cross_sections.scad
+++ b/src/cross_sections.scad
@@ -11,13 +11,14 @@
 *
 **/
 
+include <__private__/__to3d.scad>;
 include <__private__/__is_vector.scad>;
 
 function cross_sections(shape_pts, path_pts, angles, twist = 0, scale = 1.0) =
     let(
         len_path_pts_minus_one = len(path_pts) - 1,
-        sh_pts = len(shape_pts[0]) == 3 ? shape_pts : [for(p = shape_pts) [p[0], p[1], 0]],
-        pth_pts = len(path_pts[0]) == 3 ? path_pts : [for(p = path_pts) [p[0], p[1], 0]],
+        sh_pts = len(shape_pts[0]) == 3 ? shape_pts : [for(p = shape_pts) __to3d(p)],
+        pth_pts = len(path_pts[0]) == 3 ? path_pts : [for(p = path_pts) __to3d(p)],
         scale_step_vt = __is_vector(scale) ? 
             [(scale[0] - 1) / len_path_pts_minus_one, (scale[1] - 1) / len_path_pts_minus_one] :
             [(scale - 1) / len_path_pts_minus_one, (scale - 1) / len_path_pts_minus_one],
diff --git a/src/golden_spiral.scad b/src/golden_spiral.scad
index 11a1553d..0bb87957 100644
--- a/src/golden_spiral.scad
+++ b/src/golden_spiral.scad
@@ -44,12 +44,10 @@ function _golden_spiral_from_ls_or_eql_to(from, to, point_distance, rt_dir) =
         a_step = 360 / $fn * rt_dir,
         arc_points_angles = (rt_dir == 1 ? [
             for(i = [0:len_pts - 1])
-                // to 3D points because of rotate_p
-                [[circle_pts[i][0], circle_pts[i][1], 0], a_step * i] 
+                [circle_pts[i], a_step * i] 
         ] : [
             for(i = [0:len_pts - 1]) let(idx = len_pts - i - 1)
-                // to 3D points because of rotate_p
-                [[circle_pts[idx][0], circle_pts[idx][1], 0], a_step * i] 
+                [circle_pts[idx], a_step * i] 
         ]),
         offset = f2 - f1
     ) _remove_same_pts(
@@ -69,7 +67,4 @@ function _golden_spiral(from, to, point_distance, rt_dir) =
         _golden_spiral_from_ls_or_eql_to(from, to, point_distance, rt_dir) : [];
 
 function golden_spiral(from, to, point_distance, rt_dir = "CT_CLK") =    
-    [
-        for(pt_a = _golden_spiral(from, to, point_distance, (rt_dir == "CT_CLK" ? 1 : -1))) 
-            [[pt_a[0][0], pt_a[0][1]], pt_a[1]]  // to 2D points
-    ];    
\ No newline at end of file
+    _golden_spiral(from, to, point_distance, (rt_dir == "CT_CLK" ? 1 : -1));
\ No newline at end of file
diff --git a/src/path_extrude.scad b/src/path_extrude.scad
index 8370885c..a5634c83 100644
--- a/src/path_extrude.scad
+++ b/src/path_extrude.scad
@@ -16,11 +16,8 @@
 include <__private__/__is_vector.scad>;
 
 module path_extrude(shape_pts, path_pts, triangles = "RADIAL", twist = 0, scale = 1.0, closed = false) {
-
-    s_pts = to3d(shape_pts);
-    pth_pts = to3d(path_pts);
-
-    len_path_pts = len(pth_pts);    
+    
+    len_path_pts = len(path_pts);    
     len_path_pts_minus_one = len_path_pts - 1;     
 
     scale_step_vt = __is_vector(scale) ? 
@@ -31,13 +28,10 @@ module path_extrude(shape_pts, path_pts, triangles = "RADIAL", twist = 0, scale
     scale_step_y = scale_step_vt[1];
     twist_step = twist / len_path_pts_minus_one;
 
-    function to3d(pts) = 
-        len(pts[0]) == 3 ? pts : [for(p = pts) [p[0], p[1], 0]];
-
     function first_section() = 
         let(
-            p1 = pth_pts[0],
-            p2 = pth_pts[1],
+            p1 = path_pts[0], 
+            p2 = path_pts[1],
             dx = p2[0] - p1[0],
             dy = p2[1] - p1[1],
             dz = p2[2] - p1[2],
@@ -45,7 +39,7 @@ module path_extrude(shape_pts, path_pts, triangles = "RADIAL", twist = 0, scale
             az = atan2(dy, dx)
         )
         [
-            for(p = s_pts) 
+            for(p = shape_pts) 
                 rotate_p(p, [0, ay, az]) + p1
         ];
 
@@ -59,7 +53,7 @@ module path_extrude(shape_pts, path_pts, triangles = "RADIAL", twist = 0, scale
             az = atan2(dy, dx)
         )
         [
-            for(p = s_pts) 
+            for(p = shape_pts) 
                 let(scaled_p = [p[0] * (1 + scale_step_x * i), p[1] * (1 + scale_step_y * i), p[2]])
                 rotate_p(
                      rotate_p(scaled_p, twist_step * i) + [0, 0, length], 
@@ -70,11 +64,11 @@ module path_extrude(shape_pts, path_pts, triangles = "RADIAL", twist = 0, scale
     function path_extrude_inner(index) =
        index == len_path_pts ? [] :
            concat(
-               [section(pth_pts[index - 1], pth_pts[index],  index)],
+               [section(path_pts[index - 1], path_pts[index],  index)],
                path_extrude_inner(index + 1)
            );
 
-    if(closed && pth_pts[0] == pth_pts[len_path_pts_minus_one]) {
+    if(closed && path_pts[0] == path_pts[len_path_pts_minus_one]) {
         // round-robin
         sections = path_extrude_inner(1);
         polysections(
diff --git a/src/rotate_p.scad b/src/rotate_p.scad
index b7f30903..fb91f02d 100644
--- a/src/rotate_p.scad
+++ b/src/rotate_p.scad
@@ -11,6 +11,9 @@
 *
 **/ 
 
+include <__private__/__to2d.scad>;
+include <__private__/__to3d.scad>;
+
 function _rotx(pt, a) = 
     let(cosa = cos(a), sina = sin(a))
     [
@@ -38,8 +41,6 @@ function _rotz(pt, a) =
 function _rotate_p_3d(point, a) =
     _rotz(_roty(_rotx(point, a[0]), a[1]), a[2]);
 
-function _to2d(p) = [p[0], p[1]];
-
 function to_avect(a) =
      len(a) == 3 ? a : (
          len(a) == 2 ? [a[0], a[1], 0] : (
@@ -51,6 +52,6 @@ function rotate_p(point, a) =
     let(angle = to_avect(a))
     len(point) == 3 ? 
         _rotate_p_3d(point, angle) :
-        _to2d(
-            _rotate_p_3d([point[0], point[1], 0], angle)
+        __to2d(
+            _rotate_p_3d(__to3d(point), angle)
         );
diff --git a/src/shape_square.scad b/src/shape_square.scad
index 62903068..e40a183c 100644
--- a/src/shape_square.scad
+++ b/src/shape_square.scad
@@ -12,6 +12,7 @@
 *
 **/
 
+include <__private__/__is_vector.scad>;
 include <__private__/__frags.scad>;
 
 function shape_square(size, corner_r = 0) = 
@@ -20,8 +21,8 @@ function shape_square(size, corner_r = 0) =
         remain = frags % 4,
         corner_frags = (remain / 4) > 0.5 ? frags - remain + 4 : frags - remain,
         step_a = 360 / corner_frags,
-        x = len(size) == undef ? size : size[0],
-        y = len(size) == undef ? size : size[1],
+        x = __is_vector(size) ? size[0] : size,
+        y = __is_vector(size) ? size[1] : size,
         half_x = x / 2,
         half_y = y / 2, 
         half_w = half_x - corner_r,
diff --git a/src/turtle2d.scad b/src/turtle2d.scad
index e0918632..0ac58609 100644
--- a/src/turtle2d.scad
+++ b/src/turtle2d.scad
@@ -11,8 +11,6 @@
 *
 **/ 
 
-include <line2d.scad>;
-
 function _turtle2d_turtle(x, y, angle) = [[x, y], angle];
 
 function _turtle2d_set_point(turtle, point) = [point, _turtle2d_get_angle(turtle)];