implement it, don't import it

you don't understand backprop until you've written it by hand. the slowness is where the understanding lives. this is the engine behind depth before breadth.

every abstraction you import without building is a withdrawal against future understanding. it works until it doesn't, and then you have no idea why.

build it once, from scratch, badly. then the library becomes a tool you can reason about instead of magic you have to trust.

that's the whole discipline. own the foundational thing, and everything built on top of it stops being a mystery. if you skip it and ship anyway, you're just taking on debt you haven't admitted yet.