diff --git a/src/_impl/_shape_superformula_impl.scad b/src/_impl/_shape_superformula_impl.scad
new file mode 100644
index 00000000..c0356551
--- /dev/null
+++ b/src/_impl/_shape_superformula_impl.scad
@@ -0,0 +1,20 @@
+use <__comm__/__ra_to_xy.scad>;
+use <__comm__/__to_degree.scad>;
+
+function _superformula_r(angle, m1, m2, n1, n2 = 1, n3 = 1, a = 1, b = 1) = 
+    pow(
+        pow(abs(cos(m1 * angle / 4) / a), n2) + 
+        pow(abs(sin(m2 * angle / 4) / b), n3),
+        - 1 / n1    
+    );
+
+function _shape_superformula_impl(phi_step, m1, m2, n1, n2 = 1, n3 = 1, a = 1, b = 1) = 
+   let(tau = PI * 2)
+   [
+        for(phi = 0; phi <= tau; phi = phi + phi_step) 
+            let(
+                angle = __to_degree(phi),
+                r = _superformula_r(angle, m1, m2, n1, n2, n3, a, b)
+            )
+            __ra_to_xy(r, angle)
+   ];
\ No newline at end of file
diff --git a/src/shape_superformula.scad b/src/shape_superformula.scad
index 1211416c..4468aaf7 100644
--- a/src/shape_superformula.scad
+++ b/src/shape_superformula.scad
@@ -8,23 +8,7 @@
 *
 **/ 
 
-include <__comm__/__ra_to_xy.scad>;
-include <__comm__/__to_degree.scad>;
-
-function _superformula_r(angle, m1, m2, n1, n2 = 1, n3 = 1, a = 1, b = 1) = 
-    pow(
-        pow(abs(cos(m1 * angle / 4) / a), n2) + 
-        pow(abs(sin(m2 * angle / 4) / b), n3),
-        - 1 / n1    
-    );
+use <_impl/_shape_superformula_impl.scad>;
 
 function shape_superformula(phi_step, m1, m2, n1, n2 = 1, n3 = 1, a = 1, b = 1) = 
-   let(tau = PI * 2)
-   [
-        for(phi = 0; phi <= tau; phi = phi + phi_step) 
-            let(
-                angle = __to_degree(phi),
-                r = _superformula_r(angle, m1, m2, n1, n2, n3, a, b)
-            )
-            __ra_to_xy(r, angle)
-   ];
\ No newline at end of file
+   _shape_superformula_impl(phi_step, m1, m2, n1, n2, n3, a, b);
\ No newline at end of file
diff --git a/test/test_shape_superformula.scad b/test/test_shape_superformula.scad
index fe273b2c..b5a581de 100644
--- a/test/test_shape_superformula.scad
+++ b/test/test_shape_superformula.scad
@@ -1,5 +1,5 @@
-include <unittest.scad>;
-include <shape_superformula.scad>;  
+use <unittest.scad>;
+use <shape_superformula.scad>;  
 
 module test_shape_superformula() {
     echo("==== test_shape_superformula ====");