when clearing lines play voices

src/app/TetrisApp.cpp

@@ -468,6 +468,20 @@ int TetrisApp::Impl::init()
         suppressLineVoiceForLevelUp = false;
     });
 
+    // Keep co-op line-clear SFX behavior identical to classic.
+    coopGame->setSoundCallback([this, playVoiceCue](int linesCleared) {
+        if (linesCleared <= 0) {
+            return;
+        }
+
+        SoundEffectManager::instance().playSound("clear_line", 1.0f);
+
+        if (!suppressLineVoiceForLevelUp) {
+            playVoiceCue(linesCleared);
+        }
+        suppressLineVoiceForLevelUp = false;
+    });
+
     game->setLevelUpCallback([this](int /*newLevel*/) {
         if (skipNextLevelUpJingle) {
             skipNextLevelUpJingle = false;