Jim StormdancerPico-8 arranges coordinates with 0, 0 in the top left corner of the screen and y increasing as you go down. But that's a very retrocomputing-inspired design decision! Mathematicians and modern 3D engines and, like, average people looking at graphs, and even some 2D engines think 0, 0 is at the center of the screen and increasing Y means up.
My first computer was a Commodore 64, so I'm very comfortable with increasing Y meaning down. For one code base I worked on I used a graphics library that defaulted to "increasing y up" and I "fixed" it by changing the camera matrix so that increasing y was down, but that didn't fix "increasing V is up" on the texture maps so thinking about every non-trivial texture operation was a complete nightmare and now other people have to maintain that code. Sorry!
My brain is forever locked into "increasing Y is down" but I don't believe in it. I don't believe it's actually right despite using it all the time. On the other hand, I believe strongly and can articulate a specific argument that the Z axis should be up/down despite never having used in an engine that works that way.
CremAdanac@mogwai_poet If you look down at the surface of water and maintain that z should increase with depth (going away in 3d) Right hand rule dictates a Y increasing downwards. OTH if you want Z to increase with elevation Y should increase up. It's all about perspective.