The rules are simple. Make an equation, any equation in the world, that is 8 characters long, trying to guess the answer, which can also be any equation in the world. It seems like it should take dozens of tries, but with careful planning you can often guess the answer in 3 tries.
Here's the first question: What equation should you start with? That was the question I put to one class this week, and they had to think hard to justify their choice. What would you start with, and why? Perhaps you'd like to have a go? Just follow this link...
I first posted about Needle last week when I showed one student the game for the first time. Having learned a new set of strategies, today that same student totally nailed it and solved the puzzle in just two tries! By showing students that strategies work to solve any number of problems, we make them more clever mathematicians.