fixed for cooperate mode

src/app/TetrisApp.cpp

@@ -494,6 +494,17 @@ int TetrisApp::Impl::init()
         suppressLineVoiceForLevelUp = true;
     });
 
+    // Mirror single-player level-up audio/visual behavior for Coop sessions
+    coopGame->setLevelUpCallback([this](int /*newLevel*/) {
+        if (skipNextLevelUpJingle) {
+            skipNextLevelUpJingle = false;
+        } else {
+            SoundEffectManager::instance().playSound("new_level", 1.0f);
+            SoundEffectManager::instance().playSound("lets_go", 1.0f);
+        }
+        suppressLineVoiceForLevelUp = true;
+    });
+
     game->setAsteroidDestroyedCallback([](AsteroidType /*type*/) {
         SoundEffectManager::instance().playSound("asteroid_destroy", 0.9f);
     });

src/gameplay/coop/CoopGame.cpp

@@ -416,7 +416,9 @@ void CoopGame::applyLineClearRewards(PlayerState& creditPlayer, int cleared) {
     }
 
     _lines += cleared;
-    creditPlayer.lines += cleared;
+    // Credit both players with the cleared lines so cooperative play counts for both
+    left.lines += cleared;
+    right.lines += cleared;
 
     _currentCombo += 1;
     if (_currentCombo > _maxCombo) _maxCombo = _currentCombo;
@@ -445,6 +447,7 @@ void CoopGame::applyLineClearRewards(PlayerState& creditPlayer, int cleared) {
     if (targetLevel > _level) {
         _level = targetLevel;
         gravityMs = gravityMsForLevel(_level);
+        if (levelUpCallback) levelUpCallback(_level);
     }
 
     // Per-player level progression mirrors the shared rules but is driven by

src/gameplay/coop/CoopGame.h

@@ -57,7 +57,9 @@ public:
 
     explicit CoopGame(int startLevel = 0);
     using SoundCallback = std::function<void(int)>;
+    using LevelUpCallback = std::function<void(int)>;
     void setSoundCallback(SoundCallback cb) { soundCallback = cb; }
+    void setLevelUpCallback(LevelUpCallback cb) { levelUpCallback = cb; }
 
     void reset(int startLevel = 0);
     void tickGravity(double frameMs);
@@ -137,6 +139,7 @@ private:
     uint32_t hardDropFxId{0};
     uint64_t pieceSequence{0};
     SoundCallback soundCallback;
+    LevelUpCallback levelUpCallback;
 
     // Helpers ---------------------------------------------------------------
     PlayerState& player(PlayerSide s) { return s == PlayerSide::Left ? left : right; }