Add missing ID definition

app.py

@@ -27,6 +27,10 @@ def simulate_and_render(
     Returns:
         str: Path to the rendered GIF file showing the simulation from the specified viewpoint.
     """
+    global run_counter
+    run_counter += 1
+    unique_id = f"{seed}_{run_counter}_{int(time.time())}"  # Unique identifier for this run
+    
     gif_path, stability_flags, physics_state, llm_friendly_output, json_path  = run_tray_simulation(
         seed=seed,
         azimuth=azimuth,