With this machines in motion building set, children engineer their own playtime fun with the help of creative, open-ended building activities. Using the included instructions, children can build their own versions of numerous different interactive machines and vehicles, many of which incorporate special parts including a wrecking ball, chains, pulleys, and wheels. Turn out a tank with its own helicopter propeller or craft a complex contraption that spins with the twist of a lever. Children can also set the instructions aside and bring their own designs to life. Thanks to the open-ended designs and interchangeable parts, this set encourages children to discover their inner engineer and hone STEM skills such as critical thinking and trial and error. Interchangeable parts work with other Learning Resources Gears sets (sold separately) to increase the playability of every piece. Building set is designed for children ages 4 and above.