diff --git a/src/geo/polygon.js b/src/geo/polygon.js
index b7e64a4d..c2583f6e 100644
--- a/src/geo/polygon.js
+++ b/src/geo/polygon.js
@@ -2184,9 +2184,22 @@ class Polygon {
             return earcut.map(face => face.points.map(p => [ p.x, p.y, p.z ])).flat().flat();
         }
 
+        let inv = z < 0;
+
+        if (inv) {
+            z = -z;
+        }
+
         let chamfer = opt.chamfer || 0;
         let chamfer_top = opt.chamfer_top || chamfer;
         let chamfer_bottom = opt.chamfer_bottom || chamfer;
+
+        if (inv) {
+            let tmp = chamfer_top;
+            chamfer_top = chamfer_bottom;
+            chamfer_bottom = tmp;
+        }
+
         let zadd = (typeof opt === 'number' ? opt : opt.zadd || 0); // z bottom
         let obj = []; // flat output vertex array (float-x,float-y,float-z,...)
         let top_face = earcut;
@@ -2251,6 +2264,12 @@ class Polygon {
             obj.appendAll(inner.ribbonZ(rib, z_side_bottom, true));
         }
 
+        if (inv) {
+            for (let i=2; i<obj.length; i+=3) {
+                obj[i] -= z;
+            }
+        }
+
         return obj;
     }
 
diff --git a/src/main/mesh.js b/src/main/mesh.js
index a2e9dc76..892e1131 100644
--- a/src/main/mesh.js
+++ b/src/main/mesh.js
@@ -231,14 +231,15 @@ function space_init(data) {
                 case 'KeyA':
                     if (api.mode.is([ api.modes.edge ])) return mesh.edges.add();
                     return shiftKey && api.tool.analyze();
-                case 'KeyR':
-                    return shiftKey ? api.tool.rebuild() : api.tool.repair();
+                // case 'KeyR':
+                //     return shiftKey ? api.tool.rebuild() : api.tool.repair();
                 case 'KeyE':
                     if (api.mode.is([ api.modes.sketch ])) {
                         estop(evt);
                         return api.sketch.extrude();
                     }
-                    return api.tool.clean();
+                    return;
+                    // return api.tool.clean();
                 case 'KeyV':
                     return shiftKey ? selection.show() : selection.focus();
                 case 'KeyN':
diff --git a/src/mesh/sketch.js b/src/mesh/sketch.js
index 2fc773f5..cfd25590 100644
--- a/src/mesh/sketch.js
+++ b/src/mesh/sketch.js
@@ -469,7 +469,6 @@ mesh.sketch = class MeshSketch extends mesh.object {
             log('extrude', this.file || this.id, 'into', models.length, 'solid(s)');
             let { center } = this;
             let ngrp = api.group.new(models);
-            ngrp.floor();
             ngrp.move(center.x, center.y, center.z);
             // align extrusion with sketch plane
             const euler = this.group.rotation;
@@ -560,6 +559,7 @@ class SketchItem {
                 out.renderOrder = -1;
                 out.sketch_line = this;
                 out.position.z += bump + (order * bump);
+                // out.renderOrder = bump * order;
             outs.push(out);
         }
     }