Be aware that the published version is currently broken. You'll likely want to republish.

structuredClone(arr) might be more efficient?

Thanks, I wasn't aware of this function. It's probably faster, but it doesn't fix the glitch.

hachureLines appears to mutate the vertices. Another fix would be to dereference them with `arr.map(d => d.slice())`

Btw, I'd recommend importing from esm.run (or esm.sh for stubborn packages) since unpkg.com often has reliability issues.