Build time: 1 to 2 hours Difficulty level: challenging Build it: use the 172 building pieces to construct your own adorable robotic pet Hedgehog! Sound-activated: the robot has a built-in sound sensor, allowing your Hedgehog to react to different patterns of claps. Get rolling: your Hedgehog is programmed to tumble, roll, spin around, Bristle its spines, and scurry along in response to your claps-clapp once and your Hedgehog curls up into a ball and tumbles backwards one time. Clap multiple times, and it will roll again and again, tumbling once for each clap! S. T. E. M. Learning: by building your pet you'll gain experience in the inner mechanical workings that enable the Hedgehog to move the way it does; learn about gears, motors, sound sensors, LEDs (your hedgehog's eyes light up! ), and more! Battery-operated: your funny little pet Hedgehog comes with a motor that requires (4) AAA batteries (not included).