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

combat_ui.cpp

@@ -50,4 +50,9 @@ namespace gui {
     auto& meter = $gui.world().get<Meter>($meter);
     meter.percent = percent;
   }
+
+  void CombatUI::update_level(GameLevel &level) {
+    $level = level;
+    render();
+  }
 }