WIP pushing menu to game engine - improving menu text clarity in ASCII mode

Signed-off-by: Hans Kokx <hans.d.kokx@gmail.com>

apps/wolf_3d_gui/lib/screens/game_screen.dart

@@ -37,13 +37,12 @@ class _GameScreenState extends State<GameScreen> {
 
   @override
   Widget build(BuildContext context) {
-    return WillPopScope(
-      onWillPop: () async {
-        if (_engine.isDifficultySelectionPending) {
+    return PopScope<Object?>(
+      canPop: _engine.difficulty != null,
+      onPopInvokedWithResult: (didPop, result) {
+        if (!didPop && _engine.difficulty == null) {
           widget.wolf3d.input.queueBackAction();
-          return false;
         }
-        return true;
       },
       child: Scaffold(
         body: LayoutBuilder(
@@ -55,7 +54,7 @@ class _GameScreenState extends State<GameScreen> {
             return Listener(
               onPointerDown: (event) {
                 widget.wolf3d.input.onPointerDown(event);
-                if (_engine.isDifficultySelectionPending &&
+                if (_engine.difficulty == null &&
                     viewportRect.width > 0 &&
                     viewportRect.height > 0 &&
                     viewportRect.contains(event.localPosition)) {