This is a tool I made for playing around with the matrix 3d CSS function. I'm not sure if I'm any closer to understanding what the different inputs do really, but it's fun to play around with. I'm using Javascript to build the sphere of dots, then the different sliders change the values of the 16 different 3D matrix variables. The whole thing can get a little overwhelming and breaks easily, so I've added in a reset button.
You can view the project here https://projects.andrewlux.com/3dmatrix/
Download the repository and open the index.html file in your browser.