This is my second marble run. This one was a challenge. While I am patient I was able to build the entire model without any broken pieces there were a few that just didn't fit properly. A few parts of the crank portion had to be repeatedly put together and taken apart due to things not quite lining up correctly. In the end it all went together but the functionality is not up to par. The initial lift does not clear the lift to the marble stays on the lift instead of starting down the track. (Some serious sanding was required). At the drop point on the rolling drop rails, often the marble just falls and does not continue down the track. Adding my own ramp piece for the marbles to land on and get some momentum fixed this issue. I also found that the second ramp coming off the main lift was about 1 cm too long and did not fit properly. After doing a little McGyvering I was able to get the ramp to fit but it is very likely because of this, the ramp is not angled like it should and again the marbles do not run the track. Overall I enjoy building these wooden puzzles but I think this one needs a bit of reworking. As for the unit itself it looks neat but functionally it is not that good. Decide for yourself if it is worth it.