This is the second puzzle of its kind that I've purchased for my 5-year-old granddaughter. It's quite challenging but well-made, with easy-to-handle pieces. We're approaching this puzzle in stages. Initially, we set up some of the track and experimented with using the dozers to move the balls. The spring-loaded vehicle can be a bit tricky for small hands to maneuver, requiring both pulling back and holding it before setting it on the track. I believe it might be challenging for younger children who may not have developed the necessary eye-hand coordination yet. As we progressed, we engaged in problem-solving by arranging the track to create clear paths for the balls. Even with the instruction manual and step-by-step guidance, it proved to be quite tricky. An 8-year-old neighbor joined us, and she found it intriguing. Following the manual, she was able to construct several paths for the dozers. While the 5-year-old lost interest, the 8-year-old persisted for a significant amount of time and successfully moved the balls. In my assessment, this puzzle offers excellent STEM activity potential with plenty of opportunities for problem-solving. As an adult-guided activity, it's suitable for children no younger than 5 years old. I believe children aged 7-9 would thoroughly enjoy using it independently. I plan to continue using this puzzle with my granddaughter as she grows older, observing her development and progress.