diff --git a/portprotonqt/game_card.py b/portprotonqt/game_card.py
index 10a794e8..eae3d050 100644
--- a/portprotonqt/game_card.py
+++ b/portprotonqt/game_card.py
@@ -102,7 +102,7 @@ class GameCard(QFrame):
 
         self.favoriteLabel = ClickableLabel(self.coverWidget)
         self.favoriteLabel.clicked.connect(self.toggle_favorite)
-        self.is_favorite = self.name in read_favorites()
+        self.is_favorite = self.name in set(read_favorites())
         self.update_favorite_icon()
         self.favoriteLabel.raise_()
 
@@ -413,12 +413,13 @@ class GameCard(QFrame):
 
     def toggle_favorite(self):
         favorites = read_favorites()
+        favorites_set = set(favorites)
         if self.is_favorite:
-            if self.name in favorites:
+            if self.name in favorites_set:
                 favorites.remove(self.name)
             self.is_favorite = False
         else:
-            if self.name not in favorites:
+            if self.name not in favorites_set:
                 favorites.append(self.name)
             self.is_favorite = True
         save_favorites(favorites)
diff --git a/portprotonqt/game_library_manager.py b/portprotonqt/game_library_manager.py
index 858e045e..4ad8c97f 100644
--- a/portprotonqt/game_library_manager.py
+++ b/portprotonqt/game_library_manager.py
@@ -267,8 +267,9 @@ class GameLibraryManager:
                         return (fav_order, -game[10] if game[10] else 0, -game[11] if game[11] else 0)
 
                 # Quick partition: Sort favorites and non-favorites separately, then merge
-                fav_games = [g for g in games_list if g[0] in favorites]
-                non_fav_games = [g for g in games_list if g[0] not in favorites]
+                favorites_set = set(favorites)  # Convert to set for O(1) lookup
+                fav_games = [g for g in games_list if g[0] in favorites_set]
+                non_fav_games = [g for g in games_list if g[0] not in favorites_set]
                 sorted_fav = sorted(fav_games, key=partition_sort_key)
                 sorted_non_fav = sorted(non_fav_games, key=partition_sort_key)
                 sorted_games = sorted_fav + sorted_non_fav