This toy is one of the best things we've gotten for our kids in a long time. It is made of solid wood pieces which can be fit together in different patterns, allowing marbles to roll down the track and through tunnels. It sounds very simplistic, but this is its charm! Our six year old son played with it for two days straight when he got it for Christmas, and soon his two older sisters were helping think of new ways to configure the marble run. I was impressed because Quadrilla is very sturdy when it's assembled, which avoids the frustrations we sometimes see with racetracks or Lego buildings that fall apart. I give this set five stars in all areas because it teaches physics, develops imagination and fine motor skills, and teaches children that not all fun toys have a joy stick, batteries or flashing lights. We plan to add to our basic Quadrilla set in the future. We already bought extra marbles in various colors to make "teams."