Lots of stories about being bored in class and making programs, so I thought I'd share mine.

The functions feature allow you to define and graph equations with x and y. Well other variables also factor in including program defined variables such as z. That enables 3d orthographic graphs to be drawn.

Then I took it a step further and translated the results into a matrix and used that data to make real 3d projections of my graphs (or other shapes)

A bit serendipitous as my father just gave me back the calculator I used, I will be passing that down to my kids.