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This set is a fairly quick build, it only took about 3-4 hours to assemble. And while it needs minor adjustments it works fairly well. I mostly have 2 issues with this build. The first is how flimsy some of the longer, thinner pieces are. The spiral cone in the middle cracked near the bottom on me when I was installing it. The other bad part is the long ramps at the front left side. The bottom one has a tendency for the rails to not hold in place right so the balls fly off the rails, so you might need to take a thread and pull the inside rail down just a hair. But at $30 this is a pretty good build for what you pay.

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This is a very well-designed kit. The pieces pop out easily and generally fit together well. The assembly instructions are for the most part clear and well-illustrated. It has everything you need except scissors to cut some small wood sticks and two AA batteries.I do not consider this to be a simple puzzle to assemble, however. In a few cases it is difficult to know precisely how to do a specific task and/or the diagrams don't quite show things well enough. In my case I made a mistake in the motor installation and with the fly wheel. Correcting this once the error was discovered necessitated taking some things apart and reassembling them. Also, some of the pieces are very small. Any bit of a shake and you'll drop the piece, potentially into a place you can't reach. More disassembly required. I also found a few weak spots that required glue or some innovation to overcome a problem. For example, in the video you can see that the long rails that carry marbles flex. I had to add some material to one to keep the marbles from flying off the track.In the end, I was able to get it working properly with all four marbles in circulation simultaneously. However, after a short time (usually 1 to 2 minutes), something would become loose, and a marble would either fly off or stop moving, backing up other marbles that are coming along. This necessitates shutting down the motor, fixing the problem, and giving it another go.An interesting and fun project, but with frustration as well.

Bought this for my grandson's birthday. He is 10 and enjoys construction toys. He put it together easily and enjoys playing with it.

It is a beautiful display on my desk. Co-workers keep stopping by to ��watch it go��A few slots were too small so I did have to sandpaper to make parts fit.High quality, but it did take a while to finish. It was a fun project to complete with ��older�� children

Precession laser cut parts minimize work. Instructions largely clear and it works as advertised,