diff --git a/attachments.scad b/attachments.scad
index 6c4173f..a31c8f3 100644
--- a/attachments.scad
+++ b/attachments.scad
@@ -43,6 +43,9 @@ $ghost_this=false;
 $ghost=false;
 $ghosting=false;    // Ghosting is in effect, so don't apply it again
 
+$highlight_this=false;
+$highlight=false;
+
 _ANCHOR_TYPES = ["intersect","hull"];
 
 
@@ -1154,8 +1157,8 @@ module tag_this(tag)
 //   that don't use {{attachable()}} or built in modules such as
 //   - `polygon()`
 //   - `projection()`
-//   - `polyhedron()`  (or use [`vnf_polyhedron()`](vnf.scad#vnf_polyhedron))
-//   - `linear_extrude()`  (or use [`linear_sweep()`](regions.scad#linear_sweep))
+//   - `polyhedron()`  (or use {{vnf_polyhedron()}})
+//   - `linear_extrude()`  (or use {{linear_sweep()}})
 //   - `rotate_extrude()`
 //   - `surface()`
 //   - `import()`
@@ -3107,24 +3110,15 @@ module attachable(
         if (expose_tags || _is_shown()){
             if (!keep_color)
                 _color($color)
-                    if (($ghost || $ghost_this) && !$ghosting)
-                        %union(){
-                           $ghosting=true;
-                           children(0);
-                        }
-                    else children(0);
+                  _show_ghost() children(0);
             else {
                 $save_color=undef; // Force color_this() color in effect to persist for the entire object
-                    if (($ghost || $ghost_this) && !$ghosting)
-                        %union(){
-                           $ghosting=true;
-                           children(0);
-                        }
-                    else children(0);
+                _show_ghost() children(0);
             }
         }
         let(
             $ghost_this=false,
+            $highlight_this=false,
             $tag=default($save_tag,$tag),
             $save_tag=undef,
             $color=default($save_color,$color),
@@ -3134,6 +3128,26 @@ module attachable(
    }
 }
 
+module _show_highlight()
+{
+  if ($highlight || $highlight_this)
+    #children();
+  else
+    children();
+}  
+
+
+module _show_ghost()
+{  
+    if (($ghost || $ghost_this) && !$ghosting)
+        %union(){
+           $ghosting=true;
+           _show_highlight()children();
+        }
+    else _show_highlight()children();
+}
+
+
 // Function: reorient()
 // Synopsis: Calculates the transformation matrix needed to reorient an object.
 // SynTags: Trans, Path, VNF
diff --git a/color.scad b/color.scad
index d601e6f..4195c1b 100644
--- a/color.scad
+++ b/color.scad
@@ -161,21 +161,74 @@ module color_overlaps(color="red") {
     %children();
 }
 
-// Section: Setting Object Transparency
+// Section: Setting Object Modifiers
+
+
+
+
+// Module: highlight()
+// Synopsis: Sets # modifier for attachable children and their descendents.
+// SynTags: Trans
+// Topics: Attachments, Modifiers
+// See Also: highlight_this(), ghost(), ghost_this(), recolor(), color_this()
+// Usage:
+//   highlight([highlight]) CHILDREN;
+// Description:
+//   Sets the `#` modifier for the attachable children and their descendents until another {{highlight()}} or {{highlight_this()}}.
+//   By default, turns `#` on, which makes the children transparent pink and displays them even if they are subtracted from the model.
+//   Give the `false` parameter to disable the modifier and restore children to normal.  
+//   Do not mix this with user supplied `#` modifiers anywhere in the geometry tree.  
+// Arguments:
+//   highlight = If true set the descendents to use `#`; if false, disable `#` for descendents.  Default: true
+// Example(3D):
+//   highlight() cuboid(10)
+//     highlight(false) attach(RIGHT,BOT)cuboid(5);
+function highlight(highlight) = no_function("highlight");
+module highlight(highlight=true)
+{
+   $highlight=highlight;
+   children();
+}
+
+
+// Module: highlight_this()
+// Synopsis: Apply # modifier to children at a single level.
+// SynTags: Trans
+// Topics: Attachments, Modifiers
+// See Also: highlight(), ghost(), ghost_this(), recolor(), color_this()
+// Usage:
+//   highlight_this() CHILDREN;
+// Description:
+//   Applies the `#` modifier to the children at a single level, reverting to the previous highlight state for further descendents.  
+//   This works only with attachables and you cannot give the `#` operator anywhere in the geometry tree.  
+// Example(3D):
+//   highlight_this()
+//   cuboid(10)
+//      attach(TOP,BOT)cuboid(5);
+function highlight_this() = no_function("highlight_this");
+module highlight_this()
+{
+   $highlight_this=true;
+   children();
+}
+
+
+
 
 // Module: ghost()
-// Synopsis: Sets transparency for attachable children and their descendents.
+// Synopsis: Sets % modifier for attachable children and their descendents.
 // SynTags: Trans
-// Topics: Attachments
+// Topics: Attachments, Modifiers
 // See Also: ghost_this(), recolor(), color_this()
 // Usage:
 //   ghost([ghost]) CHILDREN;
 // Description:
-//   Sets the transparency for the attachable children and their descendents until another {{ghost()}} or {{ghost_this()}}.
-//   By default, turns transparency on.  Give the `false` parameter to disable transparency.
-//   Do not mix this with user supplied `%` operators anywhere in the geometry tree.  
+//   Sets the `%` modifier for the attachable children and their descendents until another {{ghost()}} or {{ghost_this()}}.
+//   By default, turns `%` on, which makes the children gray and also removes them from interaction with the model.
+//   Give the `false` parameter to disable the modifier and restore children to normal.  
+//   Do not mix this with user supplied `%` modifiers anywhere in the geometry tree.  
 // Arguments:
-//   ghost = If true set the descendents to be transparent; if false, disable transparency.  Default: true
+//   ghost = If true set the descendents to use `%`; if false, disable `%` for descendents.  Default: true
 // Example(3D):
 //   ghost() cuboid(10)
 //     ghost(false) cuboid(5);
@@ -188,14 +241,14 @@ module ghost(ghost=true)
 
 
 // Module: ghost_this()
-// Synopsis: Makes the children at a single level transparent. 
+// Synopsis: Apply % modifier to children at a single level.
 // SynTags: Trans
-// Topics: Attachments
+// Topics: Attachments, Modifiers
 // See Also: ghost(), recolor(), color_this()
 // Usage:
 //   ghost_this() CHILDREN;
 // Description:
-//   Makes the children transparent for one level, reverting to the previous transparency state for further descendents.  
+//   Applies the `%` modifier to the children at a single level, reverting to the previous ghost state for further descendents.  
 //   This works only with attachables and you cannot give the `%` operator anywhere in the geometry tree.  
 // Example(3D):
 //   ghost_this() cuboid(10)
diff --git a/math.scad b/math.scad
index 0058d02..272738a 100644
--- a/math.scad
+++ b/math.scad
@@ -1609,6 +1609,14 @@ function real_roots(p,eps=undef,tol=1e-14) =
 //    x0 = endpoint of interval to search for root
 //    x1 = second endpoint of interval to search for root
 //    tol = tolerance for solution.  Default: 1e-15
+// Example(2D): Solve x*sin(x)=4
+//    f = function (x) x*sin(x)-4;
+//    root=root_find(f, 0,25); // root = 15.2284
+//        // Graphical verification
+//    stroke([for(x=[0:25]) [x,f(x)]],width=.2);
+//    color("red")move([root,f(root)])
+//        circle(r=.25,$fn=16);
+
 
 //   The algorithm is based on Brent's method and is a combination of
 //   bisection and inverse quadratic approximation, where bisection occurs