refactor: removed GoogleLetter public index

lib/game/components/google_word.dart

@@ -53,21 +53,21 @@ class _GoogleWordController extends ComponentController<GoogleWord>
 
   static const _googleWord = 'Google';
 
-  final Set<int> _activatedIndexes = <int>{};
+  final _activatedLetters = <GoogleLetter>{};
 
-  void activate(int index) {
-    if (!_activatedIndexes.add(index)) return;
+  void activate(GoogleLetter googleLetter) {
+    if (!_activatedLetters.add(googleLetter)) return;
 
-    component.children.whereType<GoogleLetter>().elementAt(index).activate();
+    googleLetter.activate();
 
-    final activatedBonus = _activatedIndexes.length == _googleWord.length;
+    final activatedBonus = _activatedLetters.length == _googleWord.length;
     if (activatedBonus) {
       gameRef.audio.googleBonus();
       gameRef.read<GameBloc>().add(const BonusActivated(GameBonus.word));
       component.children.whereType<GoogleLetter>().forEach(
             (letter) => letter.deactivate(),
           );
-      _activatedIndexes.clear();
+      _activatedLetters.clear();
     }
   }
 }
@@ -77,8 +77,9 @@ class _GoogleLetterBallContactCallback
     extends ContactCallback<GoogleLetter, Ball> {
   @override
   void begin(GoogleLetter googleLetter, _, __) {
-    (googleLetter.parent! as GoogleWord)
-        .controller
-        .activate(googleLetter.index);
+    final parent = googleLetter.parent;
+    if (parent is GoogleWord) {
+      parent.controller.activate(googleLetter);
+    }
   }
 }

packages/pinball_components/lib/src/components/google_letter.dart

@@ -9,14 +9,11 @@ import 'package:pinball_components/pinball_components.dart';
 /// {@endtemplate}
 class GoogleLetter extends BodyComponent with InitialPosition {
   /// {@macro google_letter}
-  GoogleLetter(this.index)
+  GoogleLetter(int index)
       : _sprite = _GoogleLetterSprite(
           _GoogleLetterSprite.spritePaths[index],
         );
 
-  /// Index of the letter in the "GOOGLE" word.
-  final int index;
-
   final _GoogleLetterSprite _sprite;
 
   /// Activates this [GoogleLetter].

test/game/components/google_word_test.dart

@@ -41,10 +41,6 @@ void main() {
 
         final letters = googleWord.children.whereType<GoogleLetter>();
         expect(letters.length, equals(word.length));
-
-        for (var index = 0; index < word.length; index++) {
-          expect(letters.elementAt(index).index, equals(index));
-        }
       },
     );