diff --git a/src/geo/polygon.js b/src/geo/polygon.js
index a397bb8f..c88a06b5 100644
--- a/src/geo/polygon.js
+++ b/src/geo/polygon.js
@@ -70,7 +70,7 @@ export class Polygon {
         return bounds;
     }
 
-    getBound3D() {
+    getBounds3D() {
         let bounds = new THREE.Box3();
         for (let point of this.points) {
             bounds.expandByPoint(point);
diff --git a/src/kiri/core/conf.js b/src/kiri/core/conf.js
index 23b094ca..70e627e9 100644
--- a/src/kiri/core/conf.js
+++ b/src/kiri/core/conf.js
@@ -425,7 +425,7 @@ export const conf = {
                 camArcTolerance: 0.15,
                 camAreaSpindle: 1000,
                 camAreaTool: 1000,
-                camAreaType: "clear",
+                camAreaMode: "clear",
                 camAreaOver: 0.4,
                 camAreaDown: 1,
                 camAreaSpeed: 1000,
diff --git a/src/kiri/mode/cam/cl-ops.js b/src/kiri/mode/cam/cl-ops.js
index cfd40cc0..3cdf1dcf 100644
--- a/src/kiri/mode/cam/cl-ops.js
+++ b/src/kiri/mode/cam/cl-ops.js
@@ -678,7 +678,7 @@ export function createPopOps() {
         plunge: UC.newInput(LANG.cc_plng_s, { title: LANG.cc_plng_l, convert: toInt, units }),
         sep: UC.newBlank({ class: "pop-sep" }),
         over: UC.newInput(LANG.cc_sovr_s, { title: LANG.cc_sovr_l, convert: toFloat, bound: UC.bound(0.001, 100.0), units }),
-        down: UC.newInput(LANG.cc_sdwn_s, { title: LANG.cc_sdwn_l, convert: toFloat, bound: UC.bound(0, 100), units }),
+        down: UC.newInput(LANG.cc_sdwn_s, { title: LANG.cc_sdwn_l, convert: toFloat, bound: UC.bound(0.001, 100.0), units }),
         sep: UC.newBlank({ class: "pop-sep" }),
         expand: UC.newInput(LANG.cp_xpnd_s, { title: LANG.cp_xpnd_l, convert: toFloat, units }),
         refine: UC.newInput(LANG.cp_refi_s, { title: LANG.cp_refi_l, convert: toInt }),
diff --git a/src/kiri/mode/cam/op-area.js b/src/kiri/mode/cam/op-area.js
index ae406092..4b5ce03b 100644
--- a/src/kiri/mode/cam/op-area.js
+++ b/src/kiri/mode/cam/op-area.js
@@ -22,13 +22,16 @@ class OpArea extends CamOp {
         let { op, state } = this;
         let { tool, mode, down, over, follow, expand, plunge, smooth, tolerance } = op;
         let { ov_topz, ov_botz, ov_conv } = op;
-        let { settings, widget, zBottom, tabs, color } = state;
+        let { settings, widget, tabs, color } = state;
         let { addSlices, setToolDiam, cutTabs, healPolys, shadowAt, workarea } = state;
 
         let areaTool = new Tool(settings, tool);
         let toolDiam = areaTool.fluteDiameter();
+        let toolOver = toolDiam * over;
+        let zTop = ov_topz ? workarea.bottom_stock + ov_topz : workarea.top_stock;
+        let zBottom = ov_botz ? workarea.bottom_stock + ov_botz : workarea.bottom_stock;
 
-        zBottom = ov_botz ? workarea.bottom_stock + ov_botz : zBottom;
+        console.log({ workarea, zTop, zBottom });
 
         setToolDiam(toolDiam);
 
@@ -83,12 +86,42 @@ class OpArea extends CamOp {
 
         // process each area separately
         for (let area of polys) {
-            let bounds = area.getBound3D();
-            console.log({ area, bounds });
+            let bounds = area.getBounds3D();
 
             if (devel) newGroup().output()
-                .setLayer("areas", { line: 0xff8800 }, false)
-                .addPolys(polys);
+                .setLayer("area", { line: 0xff8800 }, false)
+                .addPolys([ area ]);
+
+            if (mode === 'clear') {
+                let zs = base_util.lerp(zTop, zBottom, down);
+                console.log({ area, bounds, zs });
+                for (let z of zs) {
+                    let layers = newGroup().output();
+                    let outs = [];
+                    let clip = [];
+                    let shadow = shadowAt(z);
+                    POLY.subtract([ area ], shadow, clip, undefined, undefined, 0);
+                    POLY.offset(clip, [ -toolDiam / 2, -toolOver ], {
+                        count: 1, outs, flat: true, z, minArea: 0
+                    });
+                    if (outs.length === 0) {
+                        break;
+                    }
+                    layers
+                        .setLayer("shadow", { line: 0x0088ff }, false)
+                        .addPolys(shadow);
+                    layers
+                        .setLayer("clear", { line: 0x88ff00 }, false)
+                        .addPolys(outs);
+                }
+
+            } else
+            if (mode === 'trace') {
+
+            } else
+            if (mode === 'surface') {
+
+            }
         }
 
         addSlices(groups);
diff --git a/src/kiri/mode/cam/slice.js b/src/kiri/mode/cam/slice.js
index e9bde765..06174696 100644
--- a/src/kiri/mode/cam/slice.js
+++ b/src/kiri/mode/cam/slice.js
@@ -229,19 +229,10 @@ export async function cam_slice(settings, widget, onupdate, ondone) {
             return cached;
         }
         // find closest shadow above and use to speed up delta shadow gen
-        let minZabove;
         let zover = Object.keys(shadows).map(v => parseFloat(v)).filter(v => v > z);
-        for (let zkey of zover) {
-            if (minZabove && zkey < minZabove) {
-                minZabove = zkey;
-            } else {
-                minZabove = zkey;
-            }
-        }
+        let minZabove = Math.min(Infinity, ...zover);
         let shadow = computeShadowAt(widget, z, minZabove);
-        if (minZabove) {
-            // const merge = shadow.length;
-            // const plus = shadows[minZabove].length;
+        if (minZabove < Infinity) {
             shadow = POLY.union([...shadow, ...shadows[minZabove]], 0.001, true);
         }
         return shadows[z] = POLY.setZ(shadow, z);