[sigvef]

Cool! Not to self-promote (no monetization or anything), but in case any one finds it helpful, I made something similar for myself to practice becoming more accurate with Wacom-style tablet pens: https://tabletpractice.arkt.is/

[camtarn]

This is great too! Being able to draw nice straight lines with a tablet pen might debatably be even more useful than drawing a perfect circle.