diff --git a/geom-exp.cpp b/geom-exp.cpp
index 4192cef0..689bb001 100644
--- a/geom-exp.cpp
+++ b/geom-exp.cpp
@@ -331,23 +331,23 @@ void ge_land_selection() {
     dialog::lastItem().color = linf[l].color;
     dialog::lastItem().value += validclasses[land_validity(l).quality_level];
     dialog::add_action([l] {
-      if(landvisited[l]) dialog::do_if_confirmed([l] {
+      if(landvisited[l]) dialog::do_if_confirmed(dual::mayboth([l] {
         stop_game_and_switch_mode(tactic::on ? rg::tactic : rg::nothing);
         firstland = specialland = l;
         start_game();
         popScreen();
-        });
+        }));
       });
     }
   dialog::addBreak(50);
   if(chaosUnlocked && !quotient && !euclid && !sphere) {
     dialog::addItem(XLAT("Chaos mode"), '1');
-    dialog::add_action([] {
+    dialog::add_action(dual::mayboth([] {
       if(chaosUnlocked) dialog::do_if_confirmed([] {
         stop_game_and_switch_mode(rg::chaos);
         start_game();
         });
-      });
+      }));
     }
   dialog::addItem(XLAT("next page"), '-');
 
@@ -355,6 +355,7 @@ void ge_land_selection() {
   validity_info();    
   dialog::addBreak(25);
   
+  dual::add_choice();  
   dialog::addBack();
   dialog::display();
   
diff --git a/hyper.h b/hyper.h
index 7ba3daeb..5d0736d8 100644
--- a/hyper.h
+++ b/hyper.h
@@ -5453,11 +5453,17 @@ namespace dual {
   // 0 = dualmode off, 1 = in dualmode (no game chosen), 2 = in dualmode (working on one of subgames)
   extern int state;
   extern int currently_loaded, main_side;
+  bool affect_both;
 
   bool movepc(int d, int subdir, bool checkonly);
   extern transmatrix player_orientation[2];
+  
+  void add_choice();
 
   bool split(reaction_t what);
+  void split_or_do(reaction_t what);
+  bool may_split(reaction_t what);
+  void may_split_or_do(reaction_t what);
   void switch_to(int i);
   void in_subscreen(reaction_t what);
   
@@ -5466,6 +5472,8 @@ namespace dual {
   
   void disable();
   void enable();
+  
+  inline reaction_t mayboth(reaction_t what) { return [=] { may_split_or_do(what); }; }
   }
 
 }
\ No newline at end of file
diff --git a/multigame.cpp b/multigame.cpp
index a49b4d41..b82c2311 100644
--- a/multigame.cpp
+++ b/multigame.cpp
@@ -281,6 +281,39 @@ namespace dual {
       }
     }
 
+  
+  void add_choice() {
+    if(!state) return;
+    dialog::addSelItem(XLAT("subgame affected"), 
+      XLAT(affect_both ? "both" : main_side == 0 ? "left" : "right"), '`');
+    dialog::add_action([] () {
+      affect_both = !affect_both;
+      if(!affect_both) {
+        main_side = !main_side;
+        switch_to(main_side);
+        }
+      });
+    }
+  
+  void split_or_do(reaction_t what) {
+    if(split(what)) return;
+    else what();
+    }
+
+  bool may_split(reaction_t what) {
+    if(state == 1 && affect_both) {
+      split(what);
+      return true;
+      }
+    return false;
+    }
+
+  void may_split_or_do(reaction_t what) {
+    if(state == 1 && affect_both) {
+      split(what);
+      }
+    else what();
+    }
   }
 
 }