me when i spend twenty minutes writing an optimised version of a function only to discover that my """optimisations""" have created a 45% slowdown

(aside: this was my first time tracing something with shading. it's still tracing, of course, but now i know how to do basic shading. all my drawings (digital paintings? ePaintings?) until now have been flat colours, save for textured clothes and hair, so that's a pretty decent improvement! oh, and here's the reference image)