I made a few games and demos on the C64 using this technique (switching colours every few raster lines). That part was easy to figure out. The hard bit to my 15

I made a few games and demos on the C64 using this technique (switching colours every few raster lines). That part was easy to figure out. The hard bit to my 15-year old self was finding the foreshortening relationship. Through trial and error I finally settled on a lookup table calculated using 1/tan(z)... which as it happens is a good approximation of the true 1/z relation for small angles. Crazy...