Start of a Lesson on X, Y, and Z

Since Second Life was down, we were asked to start drawing our lessons up to teach the kids. I am going to work on a lesson dealing with coordinate geometry. I never thought lesson construction, especially for math, could be difficult but when doing it, I have to be very basic in the way I explain stuff because I am guilty of making assumptions unconsciously of what I understand vs. what the kids understand when creating the lesson. It is going to be a lot more fun I believe to them because they will be able to interact with the lesson more than if it was written in chalk on the board or typed on a paper. I am going to use the idea of a dog retrieving a ball for them to get an understanding. Since the dog can jump up to catch the ball, I will be able to incorporate z- coordinates into the lesson. I just haven't figured out how I am going to illustrate negative z-coordinates. I have attached the beginning of the plan on ClassWeb.