After you've finally solved it once, some puzzles may still take many more attempts to master. For example, a puzzle based on invisible magnetic attraction and repulsion will continue to be a challenge until you can develop a method that will minimize trial and error. Even after it is mastered it should still invite you to explore it more. It should delight you while you watch others try, in their own way, what you've already accomplished. By watching other people attempt to solve the same puzzle, you notice that there was more than one way to come to the same solution.
Different people go about solutions in different ways.
Watching others solve a puzzle you think you know well can provide new insights. When choosing a puzzle for yourself or someone else, remember that a great puzzle will be fun before it is solved, while solving it, and after it has been solved. I'll tell you how I come up with some of my ideas and how you can come up with some of your own. First, I'll tell you what I think a puzzle is. A puzzle is some-thing that makes you think.