The 33977 Smart Tech Sound Action Tunnel Deluxe Set is a huge 91-piece BRIO World railway set combining passenger travel, freight, farming and interactive Smart Tech Sound play. At its centre is the battery-powered Record & Play Engine, which responds automatically to Action Tunnels and interactive destinations with movement, lights and sounds. The sprawling multi-level railway also includes a cargo train, bus, freight loading station, service station, bridges, farm animals and numerous accessories, making it one of the largest and most comprehensive Smart Tech Sound sets BRIO has produced.