diff --git a/attachments.scad b/attachments.scad
index 89d3214..5f3455a 100644
--- a/attachments.scad
+++ b/attachments.scad
@@ -1219,7 +1219,7 @@ module corner_profile(corners=CORNERS_ALL, except=[], r, d, convexity=10) {
 //   offset = If given, offsets the perimeter of the volume around the centerpoint.
 //   anchors = If given as a list of anchor points, allows named anchor points.
 //   two_d = If true, the attachable shape is 2D.  If false, 3D.  Default: false (3D)
-//   axis = The vector pointing along the axis of a cylinder geometry.  Default: UP
+//   axis = The vector pointing along the axis of a geometry.  Default: UP
 //   geom = If given, uses the pre-defined (via {{attach_geom()}} geometry.
 //
 // Side Effects:
@@ -1385,14 +1385,15 @@ module attachable(
     region = !is_undef(region)? region :
         !is_undef(path)? [path] :
         undef;
-    geom = is_def(geom)? geom : attach_geom(
-        size=size, size2=size2, shift=shift,
-        r=r, r1=r1, r2=r2, h=h,
-        d=d, d1=d1, d2=d2, l=l,
-        vnf=vnf, region=region, extent=extent,
-        cp=cp, offset=offset, anchors=anchors,
-        two_d=two_d, axis=axis
-    );
+    geom = is_def(geom)? geom :
+        attach_geom(
+            size=size, size2=size2, shift=shift,
+            r=r, r1=r1, r2=r2, h=h,
+            d=d, d1=d1, d2=d2, l=l,
+            vnf=vnf, region=region, extent=extent,
+            cp=cp, offset=offset, anchors=anchors,
+            two_d=two_d, axis=axis
+        );
     m = _attach_transform(anchor,spin,orient,geom);
     multmatrix(m) {
         $parent_anchor = anchor;
@@ -1499,7 +1500,7 @@ module attachable(
 //   offset = If given, offsets the perimeter of the volume around the centerpoint.
 //   anchors = If given as a list of anchor points, allows named anchor points.
 //   two_d = If true, the attachable shape is 2D.  If false, 3D.  Default: false (3D)
-//   axis = The vector pointing along the axis of a cylinder geometry.  Default: UP
+//   axis = The vector pointing along the axis of a geometry.  Default: UP
 //   p = The VNF, path, or point to transform.
 function reorient(
     anchor, spin, orient,
@@ -1528,14 +1529,15 @@ function reorient(
     )
     (anchor==CENTER && spin==0 && orient==UP && p!=undef)? p :
     let(
-        geom = is_def(geom)? geom : attach_geom(
-            size=size, size2=size2, shift=shift,
-            r=r, r1=r1, r2=r2, h=h,
-            d=d, d1=d1, d2=d2, l=l,
-            vnf=vnf, region=region, extent=extent,
-            cp=cp, offset=offset, anchors=anchors,
-            two_d=two_d, axis=axis
-        ),
+        geom = is_def(geom)? geom :
+            attach_geom(
+                size=size, size2=size2, shift=shift,
+                r=r, r1=r1, r2=r2, h=h,
+                d=d, d1=d1, d2=d2, l=l,
+                vnf=vnf, region=region, extent=extent,
+                cp=cp, offset=offset, anchors=anchors,
+                two_d=two_d, axis=axis
+            ),
         $attach_to = undef
     ) _attach_transform(anchor,spin,orient,geom,p);
 
@@ -1605,7 +1607,7 @@ function named_anchor(name, pos, orient=UP, spin=0) = [name, pos, orient, spin];
 //   offset = If given, offsets the perimeter of the volume around the centerpoint.
 //   anchors = If given as a list of anchor points, allows named anchor points.
 //   two_d = If true, the attachable shape is 2D.  If false, 3D.  Default: false (3D)
-//   axis = The vector pointing along the axis of a cylinder geometry.  Default: UP
+//   axis = The vector pointing along the axis of a geometry.  Default: UP
 //
 // Example(NORENDER): Cubical Shape
 //   geom = attach_geom(size=size);
@@ -1697,7 +1699,7 @@ function attach_geom(
             assert(is_vector(size,2))
             assert(is_num(size2))
             assert(is_num(shift))
-            ["rect", point2d(size), size2, shift, cp, offset, anchors]
+            ["trapezoid", point2d(size), size2, shift, cp, offset, anchors]
         ) : (
             let(
                 size2 = default(size2, point2d(size)),
@@ -1706,7 +1708,7 @@ function attach_geom(
             assert(is_vector(size,3))
             assert(is_vector(size2,2))
             assert(is_vector(shift,2))
-            ["cuboid", size, size2, shift, axis, cp, offset, anchors]
+            ["prismoid", size, size2, shift, axis, cp, offset, anchors]
         )
     ) : !is_undef(vnf)? (
         assert(is_vnf(vnf))
@@ -1748,11 +1750,11 @@ function attach_geom(
             assert(is_num(r2) || is_vector(r2,2))
             assert(is_num(l))
             assert(is_vector(shift,2))
-            ["cyl", r1, r2, l, shift, axis, cp, offset, anchors]
+            ["conoid", r1, r2, l, shift, axis, cp, offset, anchors]
         ) : (
             two_d? (
                 assert(is_num(r1) || is_vector(r1,2))
-                ["circle", r1, cp, offset, anchors]
+                ["ellipse", r1, cp, offset, anchors]
             ) : (
                 assert(is_num(r1) || is_vector(r1,3))
                 ["spheroid", r1, cp, offset, anchors]
@@ -1780,7 +1782,7 @@ function attach_geom(
 //   Returns true if the given attachment geometry description is for a 2D shape.
 function _attach_geom_2d(geom) =
     let( type = geom[0] )
-    type == "rect" || type == "circle" ||
+    type == "trapezoid" || type == "ellipse" ||
     type == "rgn_isect" || type == "rgn_extent";
 
 
@@ -1793,14 +1795,14 @@ function _attach_geom_2d(geom) =
 //   Returns the `[X,Y,Z]` bounding size for the given attachment geometry description.
 function _attach_geom_size(geom) =
     let( type = geom[0] )
-    type == "cuboid"? ( //size, size2, shift
+    type == "prismoid"? ( //size, size2, shift, axis
         let(
             size=geom[1], size2=geom[2], shift=point2d(geom[3]),
             maxx = max(size.x,size2.x),
             maxy = max(size.y,size2.y),
             z = size.z
         ) [maxx, maxy, z]
-    ) : type == "cyl"? ( //r1, r2, l, shift
+    ) : type == "conoid"? ( //r1, r2, l, shift
         let(
             r1=geom[1], r2=geom[2], l=geom[3],
             shift=point2d(geom[4]), axis=point3d(geom[5]),
@@ -1831,12 +1833,12 @@ function _attach_geom_size(geom) =
             mm = pointlist_bounds(flatten(geom[1])),
             delt = mm[1]-mm[0]
         ) [delt.x, delt.y, geom[2]]
-    ) : type == "rect"? ( //size, size2
+    ) : type == "trapezoid"? ( //size, size2
         let(
             size=geom[1], size2=geom[2], shift=geom[3],
             maxx = max(size.x,size2+abs(shift))
         ) [maxx, size.y]
-    ) : type == "circle"? ( //r
+    ) : type == "ellipse"? ( //r
         let( r=geom[1] )
         is_num(r)? [2,2]*r : v_mul([2,2],point2d(r))
     ) : type == "rgn_isect" || type == "rgn_extent"? ( //path
@@ -1982,37 +1984,36 @@ function _find_anchor(anchor, geom) =
         type = geom[0]
     )
     assert(is_vector(anchor),str("Invalid anchor: anchor=",anchor))
-    let(anchor = point3d(anchor))
-    anchor==CENTER? [anchor, cp, UP, 0] :
     let(
+        anchor = point3d(anchor),
         oang = (
             approx(point2d(anchor), [0,0])? 0 :
             atan2(anchor.y, anchor.x)+90
         )
     )
-    type == "cuboid"? ( //size, size2, shift
+    type == "prismoid"? ( //size, size2, shift, axis
         let(all_comps_good = [for (c=anchor) if (c!=sign(c)) 1]==[])
         assert(all_comps_good, "All components of an anchor for a cuboid/prismoid must be -1, 0, or 1")
         let(
             size=geom[1], size2=geom[2],
             shift=point2d(geom[3]), axis=point3d(geom[4]),
             anch = rot(from=axis, to=UP, p=anchor),
+            offset = rot(from=axis, to=UP, p=offset),
             h = size.z,
-            u = (anch.z+1)/2,  // u is one of 0, 0.5, or 1
+            u = (anch.z + 1) / 2,  // u is one of 0, 0.5, or 1
             axy = point2d(anch),
-            bot = point3d(v_mul(point2d(size)/2,axy),-h/2),
-            top = point3d(v_mul(point2d(size2)/2,axy)+shift,h/2),
+            bot = point3d(v_mul(point2d(size )/2, axy), -h/2),
+            top = point3d(v_mul(point2d(size2)/2, axy) + shift, h/2),
             pos = point3d(cp) + lerp(bot,top,u) + offset,
             vecs = [
-                if (anchor.x!=0) unit(rot(from=UP, to=unit([(top-bot).x,0,h]), p=[axy.x,0,0]), UP),
-                if (anchor.y!=0) unit(rot(from=UP, to=unit([0,(top-bot).y,h]), p=[0,axy.y,0]), UP),
-                if (anchor.z!=0) anch==CENTER? UP : unit([0,0,anch.z],UP)
+                if (anch.x!=0) unit(rot(from=UP, to=[(top-bot).x,0,h], p=[axy.x,0,0]), UP),
+                if (anch.y!=0) unit(rot(from=UP, to=[0,(top-bot).y,h], p=[0,axy.y,0]), UP),
+                if (anch.z!=0) anch==CENTER? UP : unit([0,0,anch.z],UP)
             ],
-            vec = unit(sum(vecs) / len(vecs)),
-            pos2 = rot(from=UP, to=axis, p=pos),
-            vec2 = rot(from=UP, to=axis, p=vec)
-        ) [anchor, pos2, vec2, oang]
-    ) : type == "cyl"? ( //r1, r2, l, shift
+            vec = anchor==CENTER? UP : rot(from=UP, to=axis, p=unit(sum(vecs) / len(vecs))),
+            pos2 = rot(from=UP, to=axis, p=pos)
+        ) [anchor, pos2, vec, oang]
+    ) : type == "conoid"? ( //r1, r2, l, shift
         assert(anchor.z == sign(anchor.z), "The Z component of an anchor for a cylinder/cone must be -1, 0, or 1")
         let(
             rr1=geom[1], rr2=geom[2], l=geom[3],
@@ -2020,6 +2021,7 @@ function _find_anchor(anchor, geom) =
             r1 = is_num(rr1)? [rr1,rr1] : point2d(rr1),
             r2 = is_num(rr2)? [rr2,rr2] : point2d(rr2),
             anch = rot(from=axis, to=UP, p=anchor),
+            offset = rot(from=axis, to=UP, p=offset),
             u = (anch.z+1)/2,
             axy = unit(point2d(anch),[0,0]),
             bot = point3d(v_mul(r1,axy), -l/2),
@@ -2027,12 +2029,12 @@ function _find_anchor(anchor, geom) =
             pos = point3d(cp) + lerp(bot,top,u) + offset,
             sidevec = rot(from=UP, to=top-bot, p=point3d(axy)),
             vvec = anch==CENTER? UP : unit([0,0,anch.z],UP),
-            vec = anch==CENTER? UP :
+            vec = anch==CENTER? CENTER :
                 approx(axy,[0,0])? unit(anch,UP) :
                 approx(anch.z,0)? sidevec :
                 unit((sidevec+vvec)/2,UP),
             pos2 = rot(from=UP, to=axis, p=pos),
-            vec2 = rot(from=UP, to=axis, p=vec)
+            vec2 = anch==CENTER? UP : rot(from=UP, to=axis, p=vec)
         ) [anchor, pos2, vec2, oang]
     ) : type == "spheroid"? ( //r
         let(
@@ -2043,9 +2045,9 @@ function _find_anchor(anchor, geom) =
             vec = unit(v_mul(r,anchor),UP)
         ) [anchor, pos, vec, oang]
     ) : type == "vnf_isect"? ( //vnf
-        let(
-            vnf=geom[1]
-        ) vnf==EMPTY_VNF? [anchor, [0,0,0], unit(anchor), 0] :
+        let( vnf=geom[1] )
+        approx(anchor,CTR)? [anchor, [0,0,0], UP, 0] :
+        vnf==EMPTY_VNF? [anchor, [0,0,0], unit(anchor), 0] :
         let(
             eps = 1/2048,
             points = vnf[0],
@@ -2093,9 +2095,9 @@ function _find_anchor(anchor, geom) =
         )
         [anchor, pos, n, oang]
     ) : type == "vnf_extent"? ( //vnf
-        let(
-            vnf=geom[1]
-        ) vnf==EMPTY_VNF? [anchor, [0,0,0], unit(anchor), 0] :
+        let( vnf=geom[1] )
+        approx(anchor,CTR)? [anchor, [0,0,0], UP, 0] :
+        vnf==EMPTY_VNF? [anchor, [0,0,0], unit(anchor,UP), 0] :
         let(
             rpts = apply(rot(from=anchor, to=RIGHT) * move(point3d(-cp)), vnf[0]),
             maxx = max(column(rpts,0)),
@@ -2104,7 +2106,7 @@ function _find_anchor(anchor, geom) =
             mpt = approx(point2d(anchor),[0,0])? [maxx,0,0] : avep,
             pos = point3d(cp) + rot(from=RIGHT, to=anchor, p=mpt)
         ) [anchor, pos, anchor, oang]
-    ) : type == "rect"? ( //size, size2, shift
+    ) : type == "trapezoid"? ( //size, size2, shift
         let(all_comps_good = [for (c=anchor) if (c!=sign(c)) 1]==[])
         assert(all_comps_good, "All components of an anchor for a rectangle/trapezoid must be -1, 0, or 1")
         let(
@@ -2127,7 +2129,7 @@ function _find_anchor(anchor, geom) =
                     unit((point3d(svec) + BACK) / 2, BACK)
                 )
         ) [anchor, pos, vec, 0]
-    ) : type == "circle"? ( //r
+    ) : type == "ellipse"? ( //r
         let(
             anchor = unit(_force_anchor_2d(anchor),[0,0]),
             r = force_list(geom[1],2),
@@ -2137,17 +2139,20 @@ function _find_anchor(anchor, geom) =
                              px = sign(anchor.x) * sqrt(1/(1/sqr(r.x) + m*m/sqr(r.y)))
                         )
                         [px,m*px],
-            vec = unit([r.y/r.x*pos.x, r.x/r.y*pos.y])
+            vec = unit([r.y/r.x*pos.x, r.x/r.y*pos.y],BACK)
         ) [anchor, point2d(cp+offset)+pos, vec, 0]
     ) : type == "rgn_isect"? ( //region
         let(
             anchor = _force_anchor_2d(anchor),
-            rgn = force_region(move(-point2d(cp), p=geom[1])),
+            rgn = force_region(move(-point2d(cp), p=geom[1]))
+        )
+        approx(anchor,[0,0])? [anchor, [0,0,0], BACK, 0] :
+        let(
             isects = [
                 for (path=rgn, t=triplet(path,true)) let(
                     seg1 = [t[0],t[1]],
                     seg2 = [t[1],t[2]],
-                    isect = line_intersection([[0,0],anchor], seg1,RAY,SEGMENT),
+                    isect = line_intersection([[0,0],anchor], seg1, RAY, SEGMENT),
                     n = is_undef(isect)? [0,1] :
                         !approx(isect, t[1])? line_normal(seg1) :
                         unit((line_normal(seg1)+line_normal(seg2))/2,[0,1]),
@@ -2164,15 +2169,16 @@ function _find_anchor(anchor, geom) =
             vec = unit(isect[2],[0,1])
         ) [anchor, pos, vec, 0]
     ) : type == "rgn_extent"? ( //region
+        let( anchor = _force_anchor_2d(anchor) )
+        approx(anchor,[0,0])? [anchor, [0,0,0], BACK, 0] :
         let(
-            anchor = _force_anchor_2d(anchor),
             rgn = force_region(geom[1]),
             rpts = rot(from=anchor, to=RIGHT, p=flatten(rgn)),
             maxx = max(column(rpts,0)),
             ys = [for (pt=rpts) if (approx(pt.x, maxx)) pt.y],            
             midy = (min(ys)+max(ys))/2,
             pos = rot(from=RIGHT, to=anchor, p=[maxx,midy])
-        ) [anchor, pos, unit(anchor), 0]
+        ) [anchor, pos, unit(anchor,BACK), 0]
     ) : type=="xrgn_extent" || type=="xrgn_isect" ? (  // extruded region
         assert(in_list(anchor.z,[-1,0,1]), "The Z component of an anchor for an extruded 2D shape must be -1, 0, or 1.")
         let(
@@ -2188,7 +2194,7 @@ function _find_anchor(anchor, geom) =
             twmat = zrot(lerp(0, -twist, u)),
             mat = shmat * scmat * twmat
         )
-        approx(anchor_xy,[0,0]) ? [anchor, apply(mat, up(anchor.z*L/2,cp)), anchor, oang] :
+        approx(anchor_xy,[0,0]) ? [anchor, apply(mat, up(anchor.z*L/2,cp)), unit(anchor, UP), oang] :
         let(
             newrgn = apply(mat, rgn),
             newgeom = attach_geom(two_d=true, region=newrgn, extent=type=="xrgn_extent", cp=cp),
diff --git a/shapes2d.scad b/shapes2d.scad
index 2060773..e79cd17 100644
--- a/shapes2d.scad
+++ b/shapes2d.scad
@@ -392,7 +392,7 @@ module ellipse(r, d, realign=false, circum=false, uniform=false, anchor=CENTER,
     ry = r.y * sc;
     attachable(anchor,spin, two_d=true, r=[rx,ry]) {
         if (uniform) {
-            assert(!circum, "Circum option not allowed when \"uniform\" is true");
+            check = assert(!circum, "Circum option not allowed when \"uniform\" is true");
             polygon(ellipse(r,realign=realign, circum=circum, uniform=true));
         }
         else if (rx < ry) {
@@ -591,7 +591,7 @@ module regular_ngon(n=6, r, d, or, od, ir, id, side, rounding=0, realign=false,
     id = is_finite(id)? id*sc : undef;
     side = is_finite(side)? side/2/sin(180/n) : undef;
     r = get_radius(r1=ir, r2=or, r=r, d1=id, d2=od, d=d, dflt=side);
-    assert(!is_undef(r), "regular_ngon(): need to specify one of r, d, or, od, ir, id, side.");
+    check = assert(!is_undef(r), "regular_ngon(): need to specify one of r, d, or, od, ir, id, side.");
     mat = ( realign? zrot(-180/n) : ident(4) ) * (
             !is_undef(align_tip)? rot(from=RIGHT, to=point2d(align_tip)) :
             !is_undef(align_side)? rot(from=RIGHT, to=point2d(align_side)) * zrot(180/n) :
@@ -828,7 +828,7 @@ function right_triangle(size=[1,1], center, anchor, spin=0) =
 module right_triangle(size=[1,1], center, anchor, spin=0) {
     size = is_num(size)? [size,size] : size;
     anchor = get_anchor(anchor, center, [-1,-1], [-1,-1]);
-    assert(is_vector(size,2));
+    check = assert(is_vector(size,2));
     path = right_triangle(size, center=true);
     attachable(anchor,spin, two_d=true, size=[size.x,size.y], size2=0, shift=-size.x/2) {
         polygon(path);
@@ -1083,10 +1083,11 @@ function star(n, r, ir, d, or, od, id, step, realign=false, align_tip, align_pit
 
 
 module star(n, r, ir, d, or, od, id, step, realign=false, align_tip, align_pit, anchor=CENTER, spin=0, atype="hull") {
-    assert(in_list(atype, _ANCHOR_TYPES), "Anchor type must be \"hull\" or \"intersect\"");
-    assert(is_undef(align_tip) || is_vector(align_tip));
-    assert(is_undef(align_pit) || is_vector(align_pit));
-    assert(is_undef(align_tip) || is_undef(align_pit), "Can only specify one of align_tip and align_pit");
+    checks =
+        assert(in_list(atype, _ANCHOR_TYPES), "Anchor type must be \"hull\" or \"intersect\"")
+        assert(is_undef(align_tip) || is_vector(align_tip))
+        assert(is_undef(align_pit) || is_vector(align_pit))
+        assert(is_undef(align_tip) || is_undef(align_pit), "Can only specify one of align_tip and align_pit");
     r = get_radius(r1=or, d1=od, r=r, d=d, dflt=undef);
     stepr = is_undef(step)? r : r*cos(180*step/n)/cos(180*(step-1)/n);
     ir = get_radius(r=ir, d=id, dflt=stepr);
@@ -1463,7 +1464,7 @@ function supershape(step=0.5, m1=4, m2, n1=1, n2, n3, a=1, b, r, d,anchor=CENTER
     ) reorient(anchor,spin, two_d=true, path=path, p=path, extent=atype=="hull");
 
 module supershape(step=0.5,m1=4,m2=undef,n1,n2=undef,n3=undef,a=1,b=undef, r=undef, d=undef, anchor=CENTER, spin=0, atype="hull") {
-    assert(in_list(atype, _ANCHOR_TYPES), "Anchor type must be \"hull\" or \"intersect\"");
+    check = assert(in_list(atype, _ANCHOR_TYPES), "Anchor type must be \"hull\" or \"intersect\"");
     path = supershape(step=step,m1=m1,m2=m2,n1=n1,n2=n2,n3=n3,a=a,b=b,r=r,d=d);
     attachable(anchor,spin,extent=atype=="hull", two_d=true, path=path) {
         polygon(path);
@@ -1498,7 +1499,7 @@ module supershape(step=0.5,m1=4,m2=undef,n1,n2=undef,n3=undef,a=1,b=undef, r=und
 // Examples(2D): Named anchors exist for the tips
 //   reuleaux_polygon(n=3, d=50) show_anchors(std=false);
 module reuleaux_polygon(n=3, r, d, anchor=CENTER, spin=0) {
-    assert(n>=3 && (n%2)==1);
+    check = assert(n>=3 && (n%2)==1);
     r = get_radius(r=r, d=d, dflt=1);
     path = reuleaux_polygon(n=n, r=r);
     anchors = [
diff --git a/shapes3d.scad b/shapes3d.scad
index ab674e1..bb9d538 100644
--- a/shapes3d.scad
+++ b/shapes3d.scad
@@ -214,7 +214,7 @@ module cuboid(
         e = _corner_edges(edges, corner);
         cnt = sum(e);
         r = first_defined([chamfer, rounding]);
-        dummy=assert(is_finite(r) && !approx(r,0));
+        dummy = assert(is_finite(r) && !approx(r,0));
         c = [r,r,r];
         m = 0.01;
         c2 = v_mul(corner,c/2);
@@ -266,15 +266,16 @@ module cuboid(
     teardrop = is_bool(teardrop)&&teardrop? 45 : teardrop;
     chamfer = approx(chamfer,0) ? undef : chamfer;
     rounding = approx(rounding,0) ? undef : rounding;
-    assert(is_vector(size,3));
-    assert(all_positive(size));
-    assert(is_undef(chamfer) || is_finite(chamfer),"chamfer must be a finite value");
-    assert(is_undef(rounding) || is_finite(rounding),"rounding must be a finite value");
-    assert(is_undef(rounding) || is_undef(chamfer), "Cannot specify nonzero value for both chamfer and rounding");
-    assert(teardrop==false || (is_finite(teardrop) && teardrop>0 && teardrop<90), "teardrop must be either false or an angle number between 0 and 90")
-    assert(is_undef(p1) || is_vector(p1));
-    assert(is_undef(p2) || is_vector(p2));
-    assert(is_bool(trimcorners));
+    checks = 
+        assert(is_vector(size,3))
+        assert(all_positive(size))
+        assert(is_undef(chamfer) || is_finite(chamfer),"chamfer must be a finite value")
+        assert(is_undef(rounding) || is_finite(rounding),"rounding must be a finite value")
+        assert(is_undef(rounding) || is_undef(chamfer), "Cannot specify nonzero value for both chamfer and rounding")
+        assert(teardrop==false || (is_finite(teardrop) && teardrop>0 && teardrop<90), "teardrop must be either false or an angle number between 0 and 90")
+        assert(is_undef(p1) || is_vector(p1))
+        assert(is_undef(p2) || is_vector(p2))
+        assert(is_bool(trimcorners));
     if (!is_undef(p1)) {
         if (!is_undef(p2)) {
             translate(pointlist_bounds([p1,p2])[0]) {
@@ -321,7 +322,7 @@ module cuboid(
                         }
                     }
                 } else if (chamfer<0) {
-                    assert(edges == EDGES_ALL || edges[2] == [0,0,0,0], "Cannot use negative chamfer with Z aligned edges.");
+                    checks = assert(edges == EDGES_ALL || edges[2] == [0,0,0,0], "Cannot use negative chamfer with Z aligned edges.");
                     ach = abs(chamfer);
                     cube(size, center=true);
 
@@ -408,7 +409,7 @@ module cuboid(
                         }
                     }
                 } else if (rounding<0) {
-                    assert(edges == EDGES_ALL || edges[2] == [0,0,0,0], "Cannot use negative rounding with Z aligned edges.");
+                    checks = assert(edges == EDGES_ALL || edges[2] == [0,0,0,0], "Cannot use negative rounding with Z aligned edges.");
                     ard = abs(rounding);
                     cube(size, center=true);
 
@@ -573,23 +574,25 @@ module prismoid(
     l, center,
     anchor, spin=0, orient=UP
 ) {
-    assert(is_num(size1) || is_vector(size1,2));
-    assert(is_num(size2) || is_vector(size2,2));
-    assert(is_num(h) || is_num(l));
-    assert(is_vector(shift,2));
-    assert(is_num(rounding) || is_vector(rounding,4), "Bad rounding argument.");
-    assert(is_undef(rounding1) || is_num(rounding1) || is_vector(rounding1,4), "Bad rounding1 argument.");
-    assert(is_undef(rounding2) || is_num(rounding2) || is_vector(rounding2,4), "Bad rounding2 argument.");
-    assert(is_num(chamfer) || is_vector(chamfer,4), "Bad chamfer argument.");
-    assert(is_undef(chamfer1) || is_num(chamfer1) || is_vector(chamfer1,4), "Bad chamfer1 argument.");
-    assert(is_undef(chamfer2) || is_num(chamfer2) || is_vector(chamfer2,4), "Bad chamfer2 argument.");
+    checks =
+        assert(is_num(size1) || is_vector(size1,2))
+        assert(is_num(size2) || is_vector(size2,2))
+        assert(is_num(h) || is_num(l))
+        assert(is_vector(shift,2))
+        assert(is_num(rounding) || is_vector(rounding,4), "Bad rounding argument.")
+        assert(is_undef(rounding1) || is_num(rounding1) || is_vector(rounding1,4), "Bad rounding1 argument.")
+        assert(is_undef(rounding2) || is_num(rounding2) || is_vector(rounding2,4), "Bad rounding2 argument.")
+        assert(is_num(chamfer) || is_vector(chamfer,4), "Bad chamfer argument.")
+        assert(is_undef(chamfer1) || is_num(chamfer1) || is_vector(chamfer1,4), "Bad chamfer1 argument.")
+        assert(is_undef(chamfer2) || is_num(chamfer2) || is_vector(chamfer2,4), "Bad chamfer2 argument.");
     eps = pow(2,-14);
     size1 = is_num(size1)? [size1,size1] : size1;
     size2 = is_num(size2)? [size2,size2] : size2;
-    assert(all_nonnegative(size1));
-    assert(all_nonnegative(size2));
-    assert(size1.x + size2.x > 0);
-    assert(size1.y + size2.y > 0);
+    checks2 = 
+        assert(all_nonnegative(size1))
+        assert(all_nonnegative(size2))
+        assert(size1.x + size2.x > 0)
+        assert(size1.y + size2.y > 0);
     s1 = [max(size1.x, eps), max(size1.y, eps)];
     s2 = [max(size2.x, eps), max(size2.y, eps)];
     rounding1 = default(rounding1, rounding);
@@ -841,8 +844,9 @@ module rect_tube(
     l
 ) {
     h = one_defined([h,l],"h,l");
-    assert(is_num(h), "l or h argument required.");
-    assert(is_vector(shift,2));
+    checks =
+        assert(is_num(h), "l or h argument required.")
+        assert(is_vector(shift,2));
     s1 = is_num(size1)? [size1, size1] :
         is_vector(size1,2)? size1 :
         is_num(size)? [size, size] :
@@ -875,15 +879,16 @@ module rect_tube(
     isize2 = is_def(is2)? is2 :
         (is_def(wall) && is_def(s2))? (s2-2*[wall,wall]) :
         undef;
-    assert(wall==undef || is_num(wall));
-    assert(size1!=undef, "Bad size/size1 argument.");
-    assert(size2!=undef, "Bad size/size2 argument.");
-    assert(isize1!=undef, "Bad isize/isize1 argument.");
-    assert(isize2!=undef, "Bad isize/isize2 argument.");
-    assert(isize1.x < size1.x, "Inner size is larger than outer size.");
-    assert(isize1.y < size1.y, "Inner size is larger than outer size.");
-    assert(isize2.x < size2.x, "Inner size is larger than outer size.");
-    assert(isize2.y < size2.y, "Inner size is larger than outer size.");
+    checks2 = 
+        assert(wall==undef || is_num(wall))
+        assert(size1!=undef, "Bad size/size1 argument.")
+        assert(size2!=undef, "Bad size/size2 argument.")
+        assert(isize1!=undef, "Bad isize/isize1 argument.")
+        assert(isize2!=undef, "Bad isize/isize2 argument.")
+        assert(isize1.x < size1.x, "Inner size is larger than outer size.")
+        assert(isize1.y < size1.y, "Inner size is larger than outer size.")
+        assert(isize2.x < size2.x, "Inner size is larger than outer size.")
+        assert(isize2.y < size2.y, "Inner size is larger than outer size.");
     anchor = get_anchor(anchor, center, BOT, BOT);
     attachable(anchor,spin,orient, size=[each size1, h], size2=size2, shift=shift) {
         diff("_H_o_L_e_")
@@ -1190,28 +1195,30 @@ module cyl(
                 fil1 = first_defined([rounding1, rounding]);
                 fil2 = first_defined([rounding2, rounding]);
                 if (chamfer != undef) {
-                    assert(chamfer <= r1,  "chamfer is larger than the r1 radius of the cylinder.");
-                    assert(chamfer <= r2,  "chamfer is larger than the r2 radius of the cylinder.");
+                    checks =
+                        assert(chamfer <= r1,  "chamfer is larger than the r1 radius of the cylinder.")
+                        assert(chamfer <= r2,  "chamfer is larger than the r2 radius of the cylinder.");
                 }
                 if (cham1 != undef) {
-                    assert(cham1 <= r1,  "chamfer1 is larger than the r1 radius of the cylinder.");
+                    check = assert(cham1 <= r1,  "chamfer1 is larger than the r1 radius of the cylinder.");
                 }
                 if (cham2 != undef) {
-                    assert(cham2 <= r2,  "chamfer2 is larger than the r2 radius of the cylinder.");
+                    check = assert(cham2 <= r2,  "chamfer2 is larger than the r2 radius of the cylinder.");
                 }
                 if (rounding != undef) {
-                    assert(rounding <= r1,  "rounding is larger than the r1 radius of the cylinder.");
-                    assert(rounding <= r2,  "rounding is larger than the r2 radius of the cylinder.");
+                    checks =
+                        assert(rounding <= r1,  "rounding is larger than the r1 radius of the cylinder.")
+                        assert(rounding <= r2,  "rounding is larger than the r2 radius of the cylinder.");
                 }
                 if (fil1 != undef) {
-                    assert(fil1 <= r1,  "rounding1 is larger than the r1 radius of the cylinder.");
+                    check = assert(fil1 <= r1,  "rounding1 is larger than the r1 radius of the cylinder.");
                 }
                 if (fil2 != undef) {
-                    assert(fil2 <= r2,  "rounding2 is larger than the r1 radius of the cylinder.");
+                    check = assert(fil2 <= r2,  "rounding2 is larger than the r1 radius of the cylinder.");
                 }
                 dy1 = abs(first_defined([cham1, fil1, 0]));
                 dy2 = abs(first_defined([cham2, fil2, 0]));
-                assert(dy1+dy2 <= l, "Sum of fillets and chamfer sizes must be less than the length of the cylinder.");
+                check = assert(dy1+dy2 <= l, "Sum of fillets and chamfer sizes must be less than the length of the cylinder.");
 
                 path = concat(
                     [[0,l/2]],
@@ -1540,9 +1547,10 @@ module tube(
     r2 = default(orr2, u_add(irr2,wall));
     ir1 = default(irr1, u_sub(orr1,wall));
     ir2 = default(irr2, u_sub(orr2,wall));
-    assert(all_defined([r1, r2, ir1, ir2]), "Must specify two of inner radius/diam, outer radius/diam, and wall width.");
-    assert(ir1 <= r1, "Inner radius is larger than outer radius.");
-    assert(ir2 <= r2, "Inner radius is larger than outer radius.");
+    checks =
+        assert(all_defined([r1, r2, ir1, ir2]), "Must specify two of inner radius/diam, outer radius/diam, and wall width.")
+        assert(ir1 <= r1, "Inner radius is larger than outer radius.")
+        assert(ir2 <= r2, "Inner radius is larger than outer radius.");
     sides = segs(max(r1,r2));
     anchor = get_anchor(anchor, center, BOT, CENTER);
     attachable(anchor,spin,orient, r1=r1, r2=r2, l=h) {
@@ -2608,7 +2616,6 @@ function _cut_interp(pathcut, path, data) =
 //   color("red")stroke(path, width=.3);
 //   kern = [1,1.2,1,1,.3,-.2,1,0,.8,1,1.1,1];
 //   path_text(path, "Example text", font="Courier", size=5, lettersize = 5/1.2, kern=kern, normal=UP);
-
 module path_text(path, text, font, size, thickness, lettersize, offset=0, reverse=false, normal, top, center=false, textmetrics=false, kern=0)
 {
   no_children($children);
@@ -2653,29 +2660,37 @@ module path_text(path, text, font, size, thickness, lettersize, offset=0, revers
   
   normpts = is_undef(normal) ? (reverse?1:-1)*column(pts,3) : _cut_interp(pts,path, normal);
   toppts = is_undef(top) ? undef : _cut_interp(pts,path,top);
-  for(i=idx(text))
-      let( tangent = pts[i][2] )
-      assert(!usetop || !approx(tangent*toppts[i],norm(top[i])*norm(tangent)),
-             str("Specified top direction parallel to path at character ",i))
-      assert(usetop || !approx(tangent*normpts[i],norm(normpts[i])*norm(tangent)),
-             str("Specified normal direction parallel to path at character ",i))
-      let(
-          adjustment = usetop ?  (tangent*toppts[i])*toppts[i]/(toppts[i]*toppts[i])
-                     : usernorm ?  (tangent*normpts[i])*normpts[i]/(normpts[i]*normpts[i])
-                     : [0,0,0]
-      )
-      move(pts[i][0])
-      if(dim==3){
-          frame_map(x=tangent-adjustment,
-                    z=usetop ? undef : normpts[i],
-                    y=usetop ? toppts[i] : undef)
-          up(offset-thickness/2)
+  for (i = idx(text)) {
+    tangent = pts[i][2];
+    checks =
+        assert(!usetop || !approx(tangent*toppts[i],norm(top[i])*norm(tangent)),
+               str("Specified top direction parallel to path at character ",i))
+        assert(usetop || !approx(tangent*normpts[i],norm(normpts[i])*norm(tangent)),
+               str("Specified normal direction parallel to path at character ",i));
+    adjustment = usetop ?  (tangent*toppts[i])*toppts[i]/(toppts[i]*toppts[i])
+               : usernorm ?  (tangent*normpts[i])*normpts[i]/(normpts[i]*normpts[i])
+               : [0,0,0];
+    move(pts[i][0]) {
+      if (dim==3) {
+        frame_map(
+          x=tangent-adjustment,
+          z=usetop ? undef : normpts[i],
+          y=usetop ? toppts[i] : undef
+        ) up(offset-thickness/2) {
           linear_extrude(height=thickness)
-          left(lsize[0]/2)text(text[i], font=font, size=size);
-     } else {
-          frame_map(x=point3d(tangent-adjustment), y=point3d(usetop ? toppts[i] : -normpts[i]))
-          left(lsize[0]/2)text(text[i], font=font, size=size);
-     }
+            left(lsize[0]/2)
+              text(text[i], font=font, size=size);
+        }
+      } else {
+          frame_map(
+            x=point3d(tangent-adjustment),
+            y=point3d(usetop ? toppts[i] : -normpts[i])
+          ) left(lsize[0]/2) {
+              text(text[i], font=font, size=size);
+          }
+      }
+    }
+  }
 }
 
 
@@ -2912,8 +2927,9 @@ module ruler(length=100, width, thickness=1, depth=3, labels=false, pipscale=1/3
              colors=["black","white"], alpha=1.0, unit=1, inch=false, anchor=LEFT+BACK+TOP, spin=0, orient=UP)
 {
     inchfactor = 25.4;
-    assert(depth<=5, "Cannot render scales smaller than depth=5");
-    assert(len(colors)==2, "colors must contain a list of exactly two colors.");
+    checks =
+        assert(depth<=5, "Cannot render scales smaller than depth=5")
+        assert(len(colors)==2, "colors must contain a list of exactly two colors.");
     length = inch ? inchfactor * length : length;
     unit = inch ? inchfactor*unit : unit;
     maxscale = is_def(maxscale)? maxscale : floor(log(length/unit-EPSILON));
diff --git a/vnf.scad b/vnf.scad
index a0b141d..e4a6cc1 100644
--- a/vnf.scad
+++ b/vnf.scad
@@ -104,6 +104,23 @@ EMPTY_VNF = [[],[]];  // The standard empty VNF with no vertices or faces.
 //   vnf2 = vnf_vertex_array(points=cap1, col_wrap=true);
 //   vnf3 = vnf_vertex_array(points=cap2, col_wrap=true, reverse=true);
 //   vnf_polyhedron([vnf1, vnf2, vnf3]);
+// Example(3D): Building a Multi-Stage Cylindrical Ramp
+//   include <BOSL2/rounding.scad>
+//   major_r = 50;
+//   groove_profile = [
+//       [-10,0], each arc(points=[[-7,0],[0,-3],[7,0]]), [10,0]
+//   ];
+//   ramp_profile = [ [-10,25], [90,25], [180,5], [190,5] ];
+//   rgroove = apply(right(major_r) * xrot(90), path3d(groove_profile));
+//   rprofile = round_corners(ramp_profile, radius=20, closed=false, $fn=72);
+//   vnf = vnf_vertex_array([
+//       for (a = [ramp_profile[0].x : 1 : last(ramp_profile).x]) let(
+//           z = lookup(a,rprofile),
+//           m = zrot(a) * up(z)
+//       )
+//       apply(m, [ [rgroove[0].x,0,-z], each rgroove, [last(rgroove).x,0,-z] ])
+//   ], caps=true, col_wrap=true, reverse=true);
+//   vnf_polyhedron(vnf, convexity=8);
 function vnf_vertex_array(
     points,
     caps, cap1, cap2,