diff --git a/src/voxel/_impl/_vx_curve_impl.scad b/src/voxel/_impl/_vx_curve_impl.scad
new file mode 100644
index 00000000..1d738d76
--- /dev/null
+++ b/src/voxel/_impl/_vx_curve_impl.scad
@@ -0,0 +1,12 @@
+use <../vx_bezier.scad>;
+
+function _vx_catmull_rom_spline_4pts(points, tightness) = 
+    let(
+        p1x_0tightness = (points[2] - points[0]) / 4 + points[1],
+        v_p1x = points[1] - p1x_0tightness,
+        p1x = p1x_0tightness + v_p1x * tightness,
+        p2x_0tightness = (points[1] - points[3]) / 4 + points[2],
+        v_p2x = points[2] - p2x_0tightness,
+        p2x = p2x_0tightness + v_p2x * tightness
+    )
+    vx_bezier(points[1], p1x, p2x, points[2]);
\ No newline at end of file
diff --git a/src/voxel/vx_curve.scad b/src/voxel/vx_curve.scad
index 2e665799..64a4df8e 100644
--- a/src/voxel/vx_curve.scad
+++ b/src/voxel/vx_curve.scad
@@ -1,17 +1,16 @@
+/**
+* vx_curve.scad
+*
+* @copyright Justin Lin, 2020
+* @license https://opensource.org/licenses/lgpl-3.0.html
+*
+* @see https://openhome.cc/eGossip/OpenSCAD/lib2x-vx_curve.html
+*
+**/ 
+
+use <_impl/_vx_curve_impl.scad>;
 use <../util/sort.scad>;
 use <../util/dedup.scad>;
-use <vx_bezier.scad>;
-
-function _vx_catmull_rom_spline_4pts(points, tightness) = 
-    let(
-        p1x_0tightness = (points[2] - points[0]) / 4 + points[1],
-        v_p1x = points[1] - p1x_0tightness,
-        p1x = p1x_0tightness + v_p1x * tightness,
-        p2x_0tightness = (points[1] - points[3]) / 4 + points[2],
-        v_p2x = points[2] - p2x_0tightness,
-        p2x = p2x_0tightness + v_p2x * tightness
-    )
-    vx_bezier(points[1], p1x, p2x, points[2]);
 
 function vx_curve(points, tightness = 0) = 
     let(