They are very fun to make as well! I've built my own mini-lib on top of this ASCII rendering library (
https://github.com/ertdfgcvb/play.core).
I design them in Monodraw, pass it through a janky converter I wrote that converts text into a json grid of characters. I then render a number of layers that get combined, which is a mix of the static art layer, and others generated from functions that spit out a similar cell based frame.
If you're interested:
https://gist.github.com/benjaminleonard/c913ddbf23fe7a70f9c2...
And for what it's worth there's this ASCII game: https://twitter.com/StoneStoryRPG