diff --git a/src/experimental/_impl/_px_surround_impl.scad b/src/experimental/_impl/_px_contour_impl.scad
similarity index 65%
rename from src/experimental/_impl/_px_surround_impl.scad
rename to src/experimental/_impl/_px_contour_impl.scad
index 96cae427..4c42ac8e 100644
--- a/src/experimental/_impl/_px_surround_impl.scad
+++ b/src/experimental/_impl/_px_contour_impl.scad
@@ -1,6 +1,6 @@
 use <util/has.scad>;
 
-function _px_surround_corner_value(pts, x, y) =
+function _px_contour_corner_value(pts, x, y) =
     let(
         c1 = has(pts, [x, y - 1], sorted = true) || has(pts, [x - 1, y - 1], sorted = true) ? 1 : 0,
         c2 = has(pts, [x - 1, y], sorted = true) || has(pts, [x - 1, y + 1], sorted = true) ? 2 : 0,
@@ -9,27 +9,27 @@ function _px_surround_corner_value(pts, x, y) =
     )
     c1 + c2 + c3 + c4;
 
-_px_surround_dir_table = [
+_px_contour_dir_table = [
     [4,  0], [6,  0], [7, 0],    // RIGHT
     [8,  1], [12, 1], [14, 1],   // DOWN
     [2,  2], [3,  2], [11, 2],   // UP
     [1,  3], [9,  3], [13, 3]    // LEFT
 ];
-function _px_surround_dir(cr_value) = 
-    lookup(cr_value, _px_surround_dir_table);
+function _px_contour_dir(cr_value) = 
+    lookup(cr_value, _px_contour_dir_table);
 
-_px_surround_nxt_offset = [
+_px_contour_nxt_offset = [
     [1,  0],   // RIGHT
     [0, -1],   // DOWN
     [0,  1],   // UP
     [-1, 0]    // LEFT
 ];
-function _px_surround_travel(pts, p, fst) = 
+function _px_contour_travel(pts, p, fst) = 
     let(
-        dir_i = _px_surround_dir(_px_surround_corner_value(pts, p[0], p[1])),
-        nxt_p = p + _px_surround_nxt_offset[dir_i]
+        dir_i = _px_contour_dir(_px_contour_corner_value(pts, p[0], p[1])),
+        nxt_p = p + _px_contour_nxt_offset[dir_i]
     )
     nxt_p == fst ? [p] :
     concat(
-        [p], _px_surround_travel(pts, nxt_p, fst)
+        [p], _px_contour_travel(pts, nxt_p, fst)
     );
diff --git a/src/experimental/demo/px_surround_demo.scad b/src/experimental/demo/px_contour_demo.scad
similarity index 78%
rename from src/experimental/demo/px_surround_demo.scad
rename to src/experimental/demo/px_contour_demo.scad
index 643f4eef..47657b7b 100644
--- a/src/experimental/demo/px_surround_demo.scad
+++ b/src/experimental/demo/px_contour_demo.scad
@@ -2,14 +2,14 @@ use <pixel/px_circle.scad>;
 use <pixel/px_polyline.scad>;
 use <shape_pentagram.scad>;
 use <hull_polyline2d.scad>;
-use <experimental/px_surround.scad>;
+use <experimental/px_contour.scad>;
 
 pts = px_circle(10, true);
 for(p = pts) {
     translate(p)
         square(1, center = true);
 }
-#hull_polyline2d(px_surround(pts), width = .1);
+#hull_polyline2d(px_contour(pts), width = .1);
 
 
 pentagram = [
@@ -23,5 +23,5 @@ translate([30, 0]) {
             linear_extrude(1, scale = 0.5) 
                 square(1, center = true);
     }
-    #hull_polyline2d(px_surround(pts2), width = .1);
+    #hull_polyline2d(px_contour(pts2), width = .1);
 }
\ No newline at end of file
diff --git a/src/experimental/px_surround.scad b/src/experimental/px_contour.scad
similarity index 57%
rename from src/experimental/px_surround.scad
rename to src/experimental/px_contour.scad
index e27f774b..6bae9188 100644
--- a/src/experimental/px_surround.scad
+++ b/src/experimental/px_contour.scad
@@ -1,10 +1,10 @@
-use <experimental/_impl/_px_surround_impl.scad>;
+use <experimental/_impl/_px_contour_impl.scad>;
 use <util/sort.scad>;
 
-function px_surround(points) = 
+function px_contour(points) = 
     let(
         // always start from the left-bottom pt
         sortedXY = sort(points, by = "vt"),
         fst = sortedXY[0] + [-1, -1]
     )
-    _px_surround_travel(sortedXY, fst, fst);
\ No newline at end of file
+    _px_contour_travel(sortedXY, fst, fst);
\ No newline at end of file