This is a project that I did for a graphics class a while back. It really helps to understand the concepts behind orthographic projections, model view and projection transformations, translations, rotations, scaling, etc. You can control various inputs in isolation, incrementing or decrementing each one at a time, and see the result on the entire graphical ecosystem. Your inputs are immediately reflected visually from the perspective of the hypothetical camera and from a world view coordinate system. The matrices are also adjusted and displayed in real-time, so that you can understand the mathematical implications, as well.