Move initialization and access to a singleton

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

lib/features/difficulty/difficulty_screen.dart

@@ -4,15 +4,13 @@ import 'package:wolf_3d_data_types/wolf_3d_data_types.dart';
 import 'package:wolf_3d_synth/wolf_3d_synth.dart';
 import 'package:wolf_dart/features/difficulty/difficulty.dart';
 import 'package:wolf_dart/features/renderer/renderer.dart';
+import 'package:wolf_dart/wolf_3d.dart';
 
 class DifficultyScreen extends StatefulWidget {
-  const DifficultyScreen(
-    this.data, {
+  const DifficultyScreen({
     super.key,
   });
 
-  final WolfensteinData data;
-
   @override
   State<DifficultyScreen> createState() => _DifficultyScreenState();
 }
@@ -21,7 +19,7 @@ class _DifficultyScreenState extends State<DifficultyScreen> {
   AudioSource? _menuMusicSource;
   SoundHandle? _menuMusicHandle;
 
-  bool get isShareware => widget.data.version == GameVersion.shareware;
+  bool get isShareware => Wolf3d.I.activeGame.version == GameVersion.shareware;
 
   @override
   void initState() {
@@ -37,9 +35,9 @@ class _DifficultyScreenState extends State<DifficultyScreen> {
     }
 
     // 2. We only want to play music if the IMF data actually exists
-    if (widget.data.music.isNotEmpty) {
+    if (Wolf3d.I.music.isNotEmpty) {
       // Get the first track (usually the menu theme "Wondering About My Loved Ones")
-      final music = widget.data.music.first;
+      final music = Wolf3d.I.music.first;
 
       // Render the hardware instructions into PCM and wrap in a WAV header
       final pcmSamples = ImfRenderer.render(music);
@@ -85,7 +83,7 @@ class _DifficultyScreenState extends State<DifficultyScreen> {
     Navigator.of(context).pushReplacement(
       MaterialPageRoute(
         builder: (_) => WolfRenderer(
-          widget.data,
+          Wolf3d.I.activeGame,
           difficulty: difficulty,
           isShareware: isShareware,
           showSpriteGallery: showGallery,