diff --git a/src/adapptlet.civet b/src/adapptlet.civet
index edec023..bfa902d 100644
--- a/src/adapptlet.civet
+++ b/src/adapptlet.civet
@@ -30,6 +30,7 @@ type Description
    usesCaptions: JoyceName[]
    klass: JoyceClass
    ends?: [GeoName, GeoName]
+   parts?: string[][]
 
 // We put both JoyceNames and GeoNames in here, pointing to each other
 // with the otherName property:
@@ -188,7 +189,8 @@ type ClassHandler = (
    args: JoyceArguments,
    index: number,
    cdata: ConstructionData,
-   colors: string[]) => Commander
+   colors: string[],
+   jname: string) => Commander
 type RGB = [number, number, number]
 type XYZ = RGB
 
@@ -274,7 +276,7 @@ function jToG(
          (args.subpoints ?= []).push depGeo
       else if depKlass is 'line'
          (args.subpoints ?= []).push ...ends ?? []
-   cmdr = classHandler[klass] name, method, args, index, cdata, colors
+   cmdr = classHandler[klass] name, method, args, index, cdata, colors, jname
    unless name is jname then cmdr.callbacks.push (api: AppletObject) =>
       api.setCaption name, jname
       api.setLabelStyle name, 3  // style CAPTION = 3
@@ -428,8 +430,10 @@ function jToG(
             console.log 'Setting label vis of', name, 'to', show if traceC
             api.setLabelVisible name, show
 
-   cdata.elements[jname] = {otherName: name, usesCaptions, klass, cmdr.ends}
-   cdata.elements[name] = {otherName: jname, usesCaptions, klass, cmdr.ends}
+   cdata.elements[jname] =
+      {otherName: name, usesCaptions, klass, cmdr.ends, cmdr.parts}
+   cdata.elements[name] =
+      {otherName: jname, usesCaptions, klass, cmdr.ends, cmdr.parts}
    cmdr
 
 function pivotListener(slider: string)
@@ -574,7 +578,7 @@ function proportionSimilar(
 // All of the detailed semantics of each available command lies in this
 // function.
 classHandler: Record<JoyceClass, ClassHandler> :=
-   point: (name, method, args, index, cdata, colors): Commander =>
+   point: (name, method, args, index, cdata, colors, jname): Commander =>
       return := freshCommander()
       {commands, callbacks, parts, auxiliaries} := return.value
       zeroVector := cdata.is3d ? 'Vector((0,0,0))' : 'Vector((0,0))'
@@ -582,7 +586,7 @@ classHandler: Record<JoyceClass, ClassHandler> :=
       aux := name + 'aUx'
       pivotable := cdata.pivot and name !== pivotData[cdata.pivot].pivot
       parts[0].push name
-      // HACK: Special-case corrections for Joyce Elements Bk XI
+      // HACK: Special-case corrections for Joyce Elements Bk XI & XII
       if cdata.title is 'XI.4'
          if name is 'Z' and method is 'fixed' and args.scalar?.length is 3
             method = 'perpendicular'
@@ -598,6 +602,18 @@ classHandler: Record<JoyceClass, ClassHandler> :=
             args.subpoints = ['B','P1','P3']
             args.plane = ['xOyPlane']
             commands.push 'B=(80,140)'
+      if cdata.title is 'XII.7'
+         if (name is 'E' and method is 'lineSlider'
+             and args.subpoints?[1] is cdata.elements['1Y'].otherName)
+            args.subpoints[1] = cdata.elements['1Z'].otherName
+      if cdata.title is 'XII.8'
+         if (name is 'M' and method is 'lineSlider'
+             and args.subpoints?[1] is cdata.elements['1Y'].otherName)
+            args.subpoints[1] = cdata.elements['1Z'].otherName
+      if cdata.title is 'XII.9'
+         if (jname is 'a' and method is 'lineSlider'
+             and args.subpoints?[1] is cdata.elements['1Y'].otherName)
+            args.subpoints[1] = cdata.elements['1Z'].otherName
       switch method
          /angle(?:Bisector|Divider)/
             {center, foot} :=
@@ -976,6 +992,11 @@ classHandler: Record<JoyceClass, ClassHandler> :=
                      'point'
                         moreParts[0].push newObj
                         api.setVisible newObj, false
+         'face'
+            unless args.polyhedron?.length is 1 then return
+            unless args.scalar?.length is 1 then return
+            element := cdata.elements[args.polyhedron[0]]
+            commands.push `${name} = ${element.parts?[2][args.scalar[0]-1]}`
          ///triangle|similar|parallelogram|application|quadrilateral
                |octagon|pentagon|hexagon///
             unless args.subpoints then return
@@ -1058,7 +1079,7 @@ classHandler: Record<JoyceClass, ClassHandler> :=
             auxiliaries.push aux + 1
             makeLinesInvisible callbacks, name
 
-   plane: (name, method, args) =>
+   plane: (name, method, args, index, cdata) =>
       return := freshCommander()
       {commands, callbacks, parts, auxiliaries} := return.value
       parts[2].push name
@@ -1166,7 +1187,7 @@ classHandler: Record<JoyceClass, ClassHandler> :=
                      'segment'
                         moreParts[1].push newObj
                      else
-                        moreParts[2].push newObj
+                        moreParts[2].splice 1,0,newObj
          /pyramid|tetrahedron/
             base .= args.polygon?[0]
             ends[0] = base or aux + 1