Do you like to play marble ? Do you like wood toy ? You're going to like this video ! We stay in the wood topic for this one cause it's mostly made in wood. If you're in a hurry, go to the end of the video around 02:20 cause it films the entire structure. It's very big and you'll see how the marble can make severals loops without human intervention : a simple but effective counterbalance system make the marble goes up.