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 & vehicles, many of which incorporate special parts including a wrecking ball, chains, pulleys, & 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 & bring their own designs to life. Thanks to the open-ended designs & interchangeable parts, this set encourages children to discover their inner engineer & hone STEM skills such as critical thinking & trial & 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 & above.