3D demo

I want to learn the math behind 3d graphics in Pico 8, not the crazy ones, but the very simple ones, I am thinking of making a game kinda like in voxatron, with a static camera and a platform. I dont even want voxels, just 2d sprites. I tried using tline, and I just messed arount until it got to something.
I would be very happy if someone showed me any sources for basic Pico 8 3d, or cool things done with tline.