Level traversal works, but it's very immediate. Next is a little 'confirm level' modal and a transition screen.

gui_fsm.hpp

@@ -19,6 +19,7 @@ namespace gui {
     ATTACKING,
     MAPPING,
     ROTATING,
+    NEXT_LEVEL,
     IDLE,
     END
   };
@@ -37,6 +38,7 @@ namespace gui {
     ATTACK,
     START_COMBAT,
     STOP_COMBAT,
+    STAIRS_DOWN,
     QUIT
   };
 
@@ -65,6 +67,7 @@ namespace gui {
       void IDLE(Event ev);
       void IN_COMBAT(Event ev);
       void COMBAT_ROTATE(Event ev);
+      void NEXT_LEVEL(Event ev);
       void END(Event ev);
 
       void try_move(int dir, bool strafe);
@@ -74,5 +77,6 @@ namespace gui {
       bool active();
       void run_systems();
       void handle_world_events();
+      void next_level();
   };
 }