minor fixes

src/app/TetrisApp.cpp

@@ -685,6 +685,13 @@ void TetrisApp::Impl::runLoop()
                 challengeClearFxOrder.push_back(idx);
             }
         }
+        // Seed FX RNG deterministically from the game's challenge seed so animations
+        // are reproducible per-run and per-level. Fall back to a random seed if game absent.
+        if (game) {
+            challengeClearFxRng.seed(game->getChallengeSeedBase() + static_cast<uint32_t>(nextLevel));
+        } else {
+            challengeClearFxRng.seed(std::random_device{}());
+        }
         std::shuffle(challengeClearFxOrder.begin(), challengeClearFxOrder.end(), challengeClearFxRng);
 
         challengeClearFxElapsedMs = 0.0;