I purchased this wooden puzzle as a birthday present for my father. He found it to be a bit of a challenge to assemble, but he enjoyed every moment of it and he told me he sometimes lost track of time while working on it. The parts are all numbered and the instructions are easy to follow; I think the fact that the parts are small, making it a bit delicate to assemble, was probably what my father found the most challenging... otherwise he still found it fun. In fact, I purchased another wooden puzzle (locomotive) for him for Christmas; these puzzles are great little projects for those cold winter nights!