diff --git a/dsc.h b/dsc.h
index 11403a8..8e951d6 100644
--- a/dsc.h
+++ b/dsc.h
@@ -39,6 +39,7 @@ public:
     Quaternion ToThe(double p);
     Quaternion Inverse(void);
     Quaternion Times(Quaternion b);
+    Quaternion MirrorZ(void);
 };
 
 class Vector {
diff --git a/file.cpp b/file.cpp
index a1a80f9..f7e752f 100644
--- a/file.cpp
+++ b/file.cpp
@@ -93,6 +93,7 @@ const SolveSpace::SaveTable SolveSpace::SAVED[] = {
     { 'g',  "Group.visible",            'b',    &(SS.sv.g.visible)            },
     { 'g',  "Group.suppress",           'b',    &(SS.sv.g.suppress)           },
     { 'g',  "Group.relaxConstraints",   'b',    &(SS.sv.g.relaxConstraints)   },
+    { 'g',  "Group.mirror",             'b',    &(SS.sv.g.mirror)             },
     { 'g',  "Group.remap",              'M',    &(SS.sv.g.remap)              },
     { 'g',  "Group.impFile",            'P',    &(SS.sv.g.impFile)            },
     { 'g',  "Group.impFileRel",         'P',    &(SS.sv.g.impFileRel)         },
diff --git a/group.cpp b/group.cpp
index 1f3dc21..972a5dd 100644
--- a/group.cpp
+++ b/group.cpp
@@ -706,6 +706,7 @@ void Group::CopyEntity(IdList<Entity,hEntity> *el,
                 en.param[6] = qvz;
             }
             en.numPoint = ep->actPoint;
+            if(mirror) en.numPoint.z *= -1;
             break;
 
         case Entity::NORMAL_N_COPY:
@@ -727,6 +728,8 @@ void Group::CopyEntity(IdList<Entity,hEntity> *el,
                 en.param[3] = qvz;
             }
             en.numNormal = ep->actNormal;
+            if(mirror) en.numNormal = en.numNormal.MirrorZ();
+
             en.point[0] = Remap(ep->point[0], remap);
             break;
 
@@ -762,6 +765,11 @@ void Group::CopyEntity(IdList<Entity,hEntity> *el,
             }
             en.numPoint = ep->actPoint;
             en.numNormal = ep->actNormal;
+            if(mirror) {
+                if(en.type != Entity::FACE_N_ROT_TRANS) oops();
+                en.numPoint.z   *= -1;
+                en.numNormal.vz *= -1;
+            }
             break;
 
         default:
diff --git a/groupmesh.cpp b/groupmesh.cpp
index 4d000ae..baaaca4 100644
--- a/groupmesh.cpp
+++ b/groupmesh.cpp
@@ -95,7 +95,8 @@ void Group::GenerateForStepAndRepeat(T *steps, T *outs) {
         if(type == TRANSLATE) {
             Vector trans = Vector::From(h.param(0), h.param(1), h.param(2));
             trans = trans.ScaledBy(ap);
-            transd.MakeFromTransformationOf(steps, trans, Quaternion::IDENTITY);
+            transd.MakeFromTransformationOf(steps,
+                trans, Quaternion::IDENTITY, false);
         } else {
             Vector trans = Vector::From(h.param(0), h.param(1), h.param(2));
             double theta = ap * SK.GetParam(h.param(3))->val;
@@ -104,7 +105,7 @@ void Group::GenerateForStepAndRepeat(T *steps, T *outs) {
             Quaternion q = Quaternion::From(c, s*axis.x, s*axis.y, s*axis.z);
             // Rotation is centered at t; so A(x - t) + t = Ax + (t - At)
             transd.MakeFromTransformationOf(steps,
-                trans.Minus(q.Rotate(trans)), q);
+                trans.Minus(q.Rotate(trans)), q, false);
         }
 
         // We need to rewrite any plane face entities to the transformed ones.
@@ -247,10 +248,10 @@ void Group::GenerateShellAndMesh(void) {
             SK.GetParam(h.param(5))->val,
             SK.GetParam(h.param(6))->val };
 
-        thisMesh.MakeFromTransformationOf(&impMesh, offset, q);
+        thisMesh.MakeFromTransformationOf(&impMesh, offset, q, mirror);
         thisMesh.RemapFaces(this, 0);
 
-        thisShell.MakeFromTransformationOf(&impShell, offset, q);
+        thisShell.MakeFromTransformationOf(&impShell, offset, q, mirror);
         thisShell.RemapFaces(this, 0);
     }
 
diff --git a/mesh.cpp b/mesh.cpp
index 51506a0..5d6f2b4 100644
--- a/mesh.cpp
+++ b/mesh.cpp
@@ -293,10 +293,19 @@ void SMesh::MakeFromAssemblyOf(SMesh *a, SMesh *b) {
     MakeFromCopyOf(b);
 }
 
-void SMesh::MakeFromTransformationOf(SMesh *a, Vector trans, Quaternion q) {
+void SMesh::MakeFromTransformationOf(SMesh *a, Vector trans, Quaternion q,
+                                               bool mirror)
+{
     STriangle *tr;
     for(tr = a->l.First(); tr; tr = a->l.NextAfter(tr)) {
         STriangle tt = *tr;
+        if(mirror) {
+            tt.a.z *= -1;
+            tt.b.z *= -1;
+            tt.c.z *= -1;
+            // The mirroring would otherwise turn a closed mesh inside out.
+            SWAP(Vector, tt.a, tt.b);
+        }
         tt.a = (q.Rotate(tt.a)).Plus(trans);
         tt.b = (q.Rotate(tt.b)).Plus(trans);
         tt.c = (q.Rotate(tt.c)).Plus(trans);
diff --git a/polygon.h b/polygon.h
index 6e81108..f0863c4 100644
--- a/polygon.h
+++ b/polygon.h
@@ -204,7 +204,8 @@ public:
     void MakeFromDifferenceOf(SMesh *a, SMesh *b);
 
     void MakeFromCopyOf(SMesh *a);
-    void MakeFromTransformationOf(SMesh *a, Vector trans, Quaternion q);
+    void MakeFromTransformationOf(SMesh *a, Vector trans, Quaternion q,
+                                    bool mirror);
     void MakeFromAssemblyOf(SMesh *a, SMesh *b);
 
     void MakeEdgesInPlaneInto(SEdgeList *sel, Vector n, double d);
diff --git a/sketch.h b/sketch.h
index c3cb479..e608717 100644
--- a/sketch.h
+++ b/sketch.h
@@ -102,6 +102,7 @@ public:
     bool        visible;
     bool        suppress;
     bool        relaxConstraints;
+    bool        mirror;
 
     bool        clean;
     bool        vvMeshClean;
diff --git a/srf/boolean.cpp b/srf/boolean.cpp
index d87b32a..93f9a98 100644
--- a/srf/boolean.cpp
+++ b/srf/boolean.cpp
@@ -687,7 +687,7 @@ void SShell::MakeFromAssemblyOf(SShell *a, SShell *b) {
     for(i = 0; i < 2; i++) {
         ab = (i == 0) ? a : b;
         for(c = ab->curve.First(); c; c = ab->curve.NextAfter(c)) {
-            cn = SCurve::FromTransformationOf(c, t, q);
+            cn = SCurve::FromTransformationOf(c, t, q, false);
             cn.source = (i == 0) ? SCurve::FROM_A : SCurve::FROM_B;
             // surfA and surfB are wrong now, and we can't fix them until
             // we've assigned IDs to the surfaces. So we'll get that later.
@@ -700,7 +700,7 @@ void SShell::MakeFromAssemblyOf(SShell *a, SShell *b) {
     for(i = 0; i < 2; i++) {
         ab = (i == 0) ? a : b;
         for(s = ab->surface.First(); s; s = ab->surface.NextAfter(s)) {
-            sn = SSurface::FromTransformationOf(s, t, q, true);
+            sn = SSurface::FromTransformationOf(s, t, q, false, true);
             // All the trim curve IDs get rewritten; we know the new handles
             // to the curves since we recorded them in the previous step.
             STrimBy *stb;
diff --git a/srf/curve.cpp b/srf/curve.cpp
index 81d4cc6..14301f4 100644
--- a/srf/curve.cpp
+++ b/srf/curve.cpp
@@ -88,10 +88,11 @@ void SBezier::GetBoundingProjd(Vector u, Vector orig,
     }
 }
 
-SBezier SBezier::TransformedBy(Vector t, Quaternion q) {
+SBezier SBezier::TransformedBy(Vector t, Quaternion q, bool mirror) {
     SBezier ret = *this;
     int i;
     for(i = 0; i <= deg; i++) {
+        if(mirror) ret.ctrl[i].z *= -1;
         ret.ctrl[i] = (q.Rotate(ret.ctrl[i])).Plus(t);
     }
     return ret;
@@ -167,7 +168,7 @@ SBezier SBezier::InPerspective(Vector u, Vector v, Vector n,
     Quaternion q = Quaternion::From(u, v);
     q = q.Inverse();
     // we want Q*(p - o) = Q*p - Q*o
-    SBezier ret = this->TransformedBy(q.Rotate(origin).ScaledBy(-1), q);
+    SBezier ret = this->TransformedBy(q.Rotate(origin).ScaledBy(-1), q, false);
     int i;
     for(i = 0; i <= deg; i++) {
         Vector4 ct = Vector4::From(ret.weight[i], ret.ctrl[i]);
@@ -427,20 +428,23 @@ void SBezierLoopSet::Clear(void) {
     l.Clear();
 }
 
-SCurve SCurve::FromTransformationOf(SCurve *a, Vector t, Quaternion q) {
+SCurve SCurve::FromTransformationOf(SCurve *a, Vector t, Quaternion q,
+                                               bool mirror)
+{
     SCurve ret;
     ZERO(&ret);
 
     ret.h = a->h;
     ret.isExact = a->isExact;
-    ret.exact = (a->exact).TransformedBy(t, q);
+    ret.exact = (a->exact).TransformedBy(t, q, mirror);
     ret.surfA = a->surfA;
     ret.surfB = a->surfB;
     
     SCurvePt *p;
     for(p = a->pts.First(); p; p = a->pts.NextAfter(p)) {
         SCurvePt pp = *p;
-        pp.p = (q.Rotate(p->p)).Plus(t);
+        if(mirror) pp.p.z *= -1;
+        pp.p = (q.Rotate(pp.p)).Plus(t);
         ret.pts.Add(&pp);
     }
     return ret;
diff --git a/srf/surface.cpp b/srf/surface.cpp
index 699553c..0f52347 100644
--- a/srf/surface.cpp
+++ b/srf/surface.cpp
@@ -133,6 +133,7 @@ SSurface SSurface::FromPlane(Vector pt, Vector u, Vector v) {
 }
 
 SSurface SSurface::FromTransformationOf(SSurface *a, Vector t, Quaternion q,
+                                        bool mirror,
                                         bool includingTrims)
 {
     SSurface ret;
@@ -147,7 +148,10 @@ SSurface SSurface::FromTransformationOf(SSurface *a, Vector t, Quaternion q,
     int i, j;
     for(i = 0; i <= 3; i++) {
         for(j = 0; j <= 3; j++) {
-            ret.ctrl[i][j] = (q.Rotate(a->ctrl[i][j])).Plus(t);
+            ret.ctrl[i][j] = a->ctrl[i][j];
+            if(mirror) ret.ctrl[i][j].z *= -1;
+            ret.ctrl[i][j] = (q.Rotate(ret.ctrl[i][j])).Plus(t);
+
             ret.weight[i][j] = a->weight[i][j];
         }
     }
@@ -156,12 +160,22 @@ SSurface SSurface::FromTransformationOf(SSurface *a, Vector t, Quaternion q,
         STrimBy *stb;
         for(stb = a->trim.First(); stb; stb = a->trim.NextAfter(stb)) {
             STrimBy n = *stb;
+            if(mirror) {
+                n.start.z  *= -1;
+                n.finish.z *= -1;
+            }
             n.start  = (q.Rotate(n.start)) .Plus(t);
             n.finish = (q.Rotate(n.finish)).Plus(t);
             ret.trim.Add(&n);
         }
     }
 
+    if(mirror) {
+        // If we mirror every surface of a shell, then it will end up inside
+        // out. So fix that here.
+        ret.Reverse();
+    }
+
     return ret;
 }
 
@@ -522,7 +536,7 @@ void SShell::MakeFromExtrusionOf(SBezierLoopSet *sbls, Vector t0, Vector t1,
             SCurve sc;
             ZERO(&sc);
             sc.isExact = true;
-            sc.exact = sb->TransformedBy(t0, Quaternion::IDENTITY);
+            sc.exact = sb->TransformedBy(t0, Quaternion::IDENTITY, false);
             (sc.exact).MakePwlInto(&(sc.pts));
             sc.surfA = hs0;
             sc.surfB = hsext;
@@ -530,7 +544,7 @@ void SShell::MakeFromExtrusionOf(SBezierLoopSet *sbls, Vector t0, Vector t1,
 
             ZERO(&sc);
             sc.isExact = true;
-            sc.exact = sb->TransformedBy(t1, Quaternion::IDENTITY);
+            sc.exact = sb->TransformedBy(t1, Quaternion::IDENTITY, false);
             (sc.exact).MakePwlInto(&(sc.pts));
             sc.surfA = hs1;
             sc.surfB = hsext;
@@ -669,7 +683,7 @@ void SShell::MakeFromRevolutionOf(SBezierLoopSet *sbls, Vector pt, Vector axis,
                 if(revs.d[j].v) {
                     ZERO(&sc);
                     sc.isExact = true;
-                    sc.exact = sb->TransformedBy(ts, qs);
+                    sc.exact = sb->TransformedBy(ts, qs, false);
                     (sc.exact).MakePwlInto(&(sc.pts));
                     sc.surfA = revs.d[j];
                     sc.surfB = revs.d[WRAP(j-1, 4)];
@@ -795,23 +809,26 @@ void SShell::MakeFromRevolutionOf(SBezierLoopSet *sbls, Vector pt, Vector axis,
 }
 
 void SShell::MakeFromCopyOf(SShell *a) {
-    MakeFromTransformationOf(a, Vector::From(0, 0, 0), Quaternion::IDENTITY);
+    MakeFromTransformationOf(a,
+        Vector::From(0, 0, 0), Quaternion::IDENTITY, false);
 }
 
-void SShell::MakeFromTransformationOf(SShell *a, Vector t, Quaternion q) {
+void SShell::MakeFromTransformationOf(SShell *a,
+                                      Vector t, Quaternion q, bool mirror)
+{
     booleanFailed = false;
 
     SSurface *s;
     for(s = a->surface.First(); s; s = a->surface.NextAfter(s)) {
         SSurface n;
-        n = SSurface::FromTransformationOf(s, t, q, true);
+        n = SSurface::FromTransformationOf(s, t, q, mirror, true);
         surface.Add(&n); // keeping the old ID
     }
 
     SCurve *c;
     for(c = a->curve.First(); c; c = a->curve.NextAfter(c)) {
         SCurve n;
-        n = SCurve::FromTransformationOf(c, t, q);
+        n = SCurve::FromTransformationOf(c, t, q, mirror);
         curve.Add(&n); // keeping the old ID
     }
 }
diff --git a/srf/surface.h b/srf/surface.h
index 764292c..06b3891 100644
--- a/srf/surface.h
+++ b/srf/surface.h
@@ -89,7 +89,7 @@ public:
     bool IsCircle(Vector axis, Vector *center, double *r);
     bool IsRational(void);
 
-    SBezier TransformedBy(Vector t, Quaternion q);
+    SBezier TransformedBy(Vector t, Quaternion q, bool mirror);
     SBezier InPerspective(Vector u, Vector v, Vector n,
                           Vector origin, double cameraTan);
 
@@ -166,7 +166,8 @@ public:
     hSSurface       surfA;
     hSSurface       surfB;
 
-    static SCurve FromTransformationOf(SCurve *a, Vector t, Quaternion q);
+    static SCurve FromTransformationOf(SCurve *a, Vector t, Quaternion q, 
+                                        bool mirror);
     SCurve MakeCopySplitAgainst(SShell *agnstA, SShell *agnstB,
                                 SSurface *srfA, SSurface *srfB);
     void RemoveShortSegments(SSurface *srfA, SSurface *srfB);
@@ -235,7 +236,8 @@ public:
     static SSurface FromRevolutionOf(SBezier *sb, Vector pt, Vector axis,
                                         double thetas, double thetaf);
     static SSurface FromPlane(Vector pt, Vector u, Vector v);
-    static SSurface FromTransformationOf(SSurface *a, Vector t, Quaternion q, 
+    static SSurface FromTransformationOf(SSurface *a, Vector t, Quaternion q,
+                                         bool mirror,
                                          bool includingTrims);
 
     void EdgeNormalsWithinSurface(Point2d auv, Point2d buv,
@@ -358,7 +360,8 @@ public:
                       Vector edge_n_in, Vector edge_n_out, Vector surf_n);
 
     void MakeFromCopyOf(SShell *a);
-    void MakeFromTransformationOf(SShell *a, Vector trans, Quaternion q);
+    void MakeFromTransformationOf(SShell *a, Vector trans, Quaternion q,
+                                    bool mirror);
     void MakeFromAssemblyOf(SShell *a, SShell *b);
     void MergeCoincidentSurfaces(void);
 
diff --git a/textscreens.cpp b/textscreens.cpp
index d575cd9..e5f5015 100644
--- a/textscreens.cpp
+++ b/textscreens.cpp
@@ -203,64 +203,51 @@ void TextWindow::ScreenSelectRequest(int link, DWORD v) {
     SS.GW.ClearSelection();
     SS.GW.selection[0].entity = hr.entity(0);
 }
-void TextWindow::ScreenChangeOneOrTwoSides(int link, DWORD v) {
-    SS.UndoRemember();
 
+void TextWindow::ScreenChangeGroupOption(int link, DWORD v) {
+    SS.UndoRemember();
     Group *g = SK.GetGroup(SS.TW.shown.group);
-    if(g->subtype == Group::ONE_SIDED) {
-        g->subtype = Group::TWO_SIDED;
-    } else if(g->subtype == Group::TWO_SIDED) {
-        g->subtype = Group::ONE_SIDED;
-    } else oops();
+
+    switch(link) {
+        case 's':
+            if(g->subtype == Group::ONE_SIDED) {
+                g->subtype = Group::TWO_SIDED;
+            } else {
+                g->subtype = Group::ONE_SIDED;
+            }
+            break;
+
+        case 'k':
+            (g->skipFirst) = !(g->skipFirst);
+            break;
+
+        case 'c':
+            g->meshCombine = v;
+            break;
+
+        case 'P':
+            g->suppress = !(g->suppress);
+            break;
+
+        case 'm':
+            g->mirror = !(g->mirror);
+            break;
+
+        case 'r':
+            g->relaxConstraints = !(g->relaxConstraints);
+            break;
+
+        case 'f':
+            g->forceToMesh = !(g->forceToMesh);
+            break;
+
+    }
+
     SS.MarkGroupDirty(g->h);
     SS.GenerateAll();
     SS.GW.ClearSuper();
 }
-void TextWindow::ScreenChangeSkipFirst(int link, DWORD v) {
-    SS.UndoRemember();
 
-    Group *g = SK.GetGroup(SS.TW.shown.group);
-    (g->skipFirst) = !(g->skipFirst);
-    SS.MarkGroupDirty(g->h);
-    SS.GenerateAll();
-    SS.GW.ClearSuper();
-}
-void TextWindow::ScreenChangeMeshCombine(int link, DWORD v) {
-    SS.UndoRemember();
-
-    Group *g = SK.GetGroup(SS.TW.shown.group);
-    g->meshCombine = v;
-    SS.MarkGroupDirty(g->h);
-    SS.GenerateAll();
-    SS.GW.ClearSuper();
-}
-void TextWindow::ScreenChangeMeshOrExact(int link, DWORD v) {
-    SS.UndoRemember();
-
-    Group *g = SK.GetGroup(SS.TW.shown.group);
-    g->forceToMesh = !(g->forceToMesh);
-    SS.MarkGroupDirty(g->h);
-    SS.GenerateAll();
-    SS.GW.ClearSuper();
-}
-void TextWindow::ScreenChangeSuppress(int link, DWORD v) {
-    SS.UndoRemember();
-
-    Group *g = SK.GetGroup(SS.TW.shown.group);
-    g->suppress = !(g->suppress);
-    SS.MarkGroupDirty(g->h);
-    SS.GenerateAll();
-    SS.GW.ClearSuper();
-}
-void TextWindow::ScreenChangeRelaxConstraints(int link, DWORD v) {
-    SS.UndoRemember();
-
-    Group *g = SK.GetGroup(SS.TW.shown.group);
-    g->relaxConstraints = !(g->relaxConstraints);
-    SS.MarkGroupDirty(g->h);
-    SS.later.generateAll = true;
-    SS.later.showTW = true;
-}
 void TextWindow::ScreenChangeRightLeftHanded(int link, DWORD v) {
     SS.UndoRemember();
 
@@ -367,10 +354,10 @@ void TextWindow::ShowGroupInfo(void) {
        g->type == Group::TRANSLATE)
     {
         bool one = (g->subtype == Group::ONE_SIDED);
-        Printf(true, "%Ft%s%E %Fh%f%Ll%s%E%Fs%s%E / %Fh%f%Ll%s%E%Fs%s%E", s,
-            &TextWindow::ScreenChangeOneOrTwoSides,
+        Printf(true, "%Ft%s%E %Fh%f%Ls%s%E%Fs%s%E / %Fh%f%Ls%s%E%Fs%s%E", s,
+            &TextWindow::ScreenChangeGroupOption,
             (one ? "" : "one side"), (one ? "one side" : ""),
-            &TextWindow::ScreenChangeOneOrTwoSides,
+            &TextWindow::ScreenChangeGroupOption,
             (!one ? "" : "two sides"), (!one ? "two sides" : ""));
     } 
     
@@ -402,11 +389,11 @@ void TextWindow::ShowGroupInfo(void) {
         bool space;
         if(g->subtype == Group::ONE_SIDED) {
             bool skip = g->skipFirst;
-            Printf(true, "%Ft%s%E %Fh%f%Ll%s%E%Fs%s%E / %Fh%f%Ll%s%E%Fs%s%E",
+            Printf(true, "%Ft%s%E %Fh%f%Lk%s%E%Fs%s%E / %Fh%f%Lk%s%E%Fs%s%E",
                 s3,
-                &ScreenChangeSkipFirst,
+                &ScreenChangeGroupOption,
                 (!skip ? "" : "with original"), (!skip ? "with original" : ""),
-                &ScreenChangeSkipFirst,
+                &ScreenChangeGroupOption,
                 (skip ? "":"with copy #1"), (skip ? "with copy #1":""));
             space = false;
         } else {
@@ -435,34 +422,40 @@ void TextWindow::ShowGroupInfo(void) {
         bool asa  = (g->type == Group::IMPORTED);
 
         Printf((g->type == Group::HELICAL_SWEEP),
-            "%FtMERGE AS%E %Fh%f%D%Ll%s%E%Fs%s%E / %Fh%f%D%Ll%s%E%Fs%s%E %s "
-            "%Fh%f%D%Ll%s%E%Fs%s%E",
-            &TextWindow::ScreenChangeMeshCombine,
+            "%FtMERGE AS%E %Fh%f%D%Lc%s%E%Fs%s%E / %Fh%f%D%Lc%s%E%Fs%s%E %s "
+            "%Fh%f%D%Lc%s%E%Fs%s%E",
+            &TextWindow::ScreenChangeGroupOption,
             Group::COMBINE_AS_UNION,
             (un ? "" : "union"), (un ? "union" : ""),
-            &TextWindow::ScreenChangeMeshCombine,
+            &TextWindow::ScreenChangeGroupOption,
             Group::COMBINE_AS_DIFFERENCE,
             (diff ? "" : "difference"), (diff ? "difference" : ""),
             asa ? "/" : "",
-            &TextWindow::ScreenChangeMeshCombine,
+            &TextWindow::ScreenChangeGroupOption,
             Group::COMBINE_AS_ASSEMBLE,
             (asy || !asa ? "" : "assemble"), (asy && asa ? "assemble" : ""));
     }
     if(g->type == Group::IMPORTED) {
         bool sup = g->suppress;
-        Printf(false, "%FtSUPPRESS%E %Fh%f%Ll%s%E%Fs%s%E / %Fh%f%Ll%s%E%Fs%s%E",
-            &TextWindow::ScreenChangeSuppress,
+        Printf(false, "%FtSUPPRESS%E %Fh%f%LP%s%E%Fs%s%E / %Fh%f%LP%s%E%Fs%s%E",
+            &TextWindow::ScreenChangeGroupOption,
             (sup ? "" : "yes"), (sup ? "yes" : ""),
-            &TextWindow::ScreenChangeSuppress,
+            &TextWindow::ScreenChangeGroupOption,
             (!sup ? "" : "no"), (!sup ? "no" : ""));
+
+        Printf(false, "%FtMIRROR%E   %Fh%f%Lm%s%E%Fs%s%E / %Fh%f%Lm%s%E%Fs%s%E",
+            &TextWindow::ScreenChangeGroupOption,
+            (g->mirror ? "" : "yes"), (g->mirror ? "yes" : ""),
+            &TextWindow::ScreenChangeGroupOption,
+            (!g->mirror ? "" : "no"), (!g->mirror ? "no" : ""));
     }
 
     bool relax = g->relaxConstraints;
-    Printf(true, "%FtSOLVING%E  %Fh%f%Ll%s%E%Fs%s%E / %Fh%f%Ll%s%E%Fs%s%E",
-        &TextWindow::ScreenChangeRelaxConstraints,
+    Printf(true, "%FtSOLVING%E  %Fh%f%Lr%s%E%Fs%s%E / %Fh%f%Lr%s%E%Fs%s%E",
+        &TextWindow::ScreenChangeGroupOption,
         (!relax ? "" : "with all constraints"),
              (!relax ? "with all constraints" : ""),
-        &TextWindow::ScreenChangeRelaxConstraints,
+        &TextWindow::ScreenChangeGroupOption,
         (relax ? "" : "no"), (relax ? "no" : ""));
 
     if(g->type == Group::EXTRUDE ||
@@ -490,10 +483,10 @@ void TextWindow::ShowGroupInfo(void) {
         if(pg->runningMesh.IsEmpty() && g->thisMesh.IsEmpty()) {
             bool fm = g->forceToMesh;
             Printf(true,
-                "%FtSURFACES%E %Fh%f%Ll%s%E%Fs%s%E / %Fh%f%Ll%s%E%Fs%s%E",
-                    &TextWindow::ScreenChangeMeshOrExact,
+                "%FtSURFACES%E %Fh%f%Lf%s%E%Fs%s%E / %Fh%f%Lf%s%E%Fs%s%E",
+                    &TextWindow::ScreenChangeGroupOption,
                     (!fm ? "" : "as NURBS"), (!fm ? "as NURBS" : ""),
-                    &TextWindow::ScreenChangeMeshOrExact,
+                    &TextWindow::ScreenChangeGroupOption,
                     (fm ? "" : "as mesh"), (fm ? "as mesh" : ""));
         } else {
             Printf(false,
diff --git a/ui.h b/ui.h
index 6821790..ce372c6 100644
--- a/ui.h
+++ b/ui.h
@@ -147,12 +147,7 @@ public:
     static void ScreenSelectRequest(int link, DWORD v);
     static void ScreenSelectConstraint(int link, DWORD v);
 
-    static void ScreenChangeOneOrTwoSides(int link, DWORD v);
-    static void ScreenChangeSkipFirst(int link, DWORD v);
-    static void ScreenChangeMeshCombine(int link, DWORD v);
-    static void ScreenChangeMeshOrExact(int link, DWORD v);
-    static void ScreenChangeSuppress(int link, DWORD v);
-    static void ScreenChangeRelaxConstraints(int link, DWORD v);
+    static void ScreenChangeGroupOption(int link, DWORD v);
     static void ScreenChangeRightLeftHanded(int link, DWORD v);
     static void ScreenChangeHelixParameter(int link, DWORD v);
     static void ScreenColor(int link, DWORD v);
diff --git a/util.cpp b/util.cpp
index 02fd0b1..bfa207c 100644
--- a/util.cpp
+++ b/util.cpp
@@ -290,6 +290,14 @@ Quaternion Quaternion::Times(Quaternion b) {
     return r;
 }
 
+Quaternion Quaternion::MirrorZ(void) {
+    Vector u = RotationU(),
+           v = RotationV();
+    u.z *= -1;
+    v.z *= -1;
+    return Quaternion::From(u, v);
+}
+
 
 Vector Vector::From(double x, double y, double z) {
     Vector v;
diff --git a/wishlist.txt b/wishlist.txt
index 95630ab..0a30abd 100644
--- a/wishlist.txt
+++ b/wishlist.txt
@@ -2,17 +2,16 @@
 multi-drag
 copy and paste
 wireframe export
-import mirrored
+interpolating splines
+associative entities from solid model, as a special group
 
 -----
 some kind of import
 filled contours for export
 faster triangulation
-interpolating splines
 loop detection
 IGES export
 incremental regen of entities
-associative entities from solid model, as a special group
 rounding, as a special group