marble run

The marble runs are intricate. Sam builds them from pictures on the box. Sometimes he can detect when they're just slightly off and gets very upset. I told him that grown-ups have a very hard time stepping back from their work and being critical, so that is a very good skill. The key is to not get so upset that you can't discern what the problem is. He should be very proud that he can detect flaws, because that is the first step in mastery.