@neauoire That's looking pretty awesome already. It reminds me a bit of an 1bit mac program for Japanese caligraphy (https://www.macintoshrepository.org/14703-macintosh-calligraphy).
It didn't work that great when emulating, but the idea behind it (the faster you move the mouse, the thinner the line gets) felt like a solid solution to get caligraphic lines only with the mouse.
@FredBednarski oh wow, they really leaned into the brush thing. This is giving me ideas, thanks for sharing this :)