Our preschoolers adore this toy! The pieces and gears are simple enough to put together - Even a 3yr old can make a moveable unit. Like Legos, some of the pieces can be harder to take apart, but I think that's fine, and about par for the course. The prongs on the red connector pieces can break, which is why I gave it a 4 for durability. If they can remedy that, this would be one of the few toys that I would rate this highly. I like that younger kids probably need a little help, as it gets the parents in on the play, too. And we don't mind! It's imaginative, creative, and teaches some basic mechanics. Our kids also don't mind cleaning it up, because it's got the wonderfully designed tool box. I wish all toys came with their own storage! The hardest part is getting them to put it down for a while. Great idea.