Great product, same principle as the ball puzzles. The pieces are numbered and the arrows indicate the order in which to put them. It took me about 1 hour to finish it. And yes the problem is that once you start, you want to finish it to see what happens in the end. Most important difficulty when mounting the top floor because the parts are becoming closer and it is difficult to smooth that it's still pretty.
Overall very good product but to make it more educational, the system should be removed even if it seems impossible numbers because the patterns are identical on all four sides.
Treat yourself, you will enjoy your time to assemble this puzzle.
