Some people build simple stuff using K’Nex, but others like to build huge contraptions like this. This is The Citadel, a huge K’nex ball moving machine built by YouTuber Shadowman. It took him about 3 years to build it.
Look at this crazy K’Nex machine. It took 8 months to create, has over 450 feet of track and it includes over 40,000 K’Nex pieces, 8 motors, 5 lifts, 21 distinct paths, and a computer-controlled crane.