And, of course, Futilitris: https://tetris.wiki/Futilitris

Wow, that's really cool game. That feeling of mathematical difficulty when you're playing is very cool.

I just went down a rabbit hole with this excellent blog post on using data structures, search algorithms, and maybe some machine learning to try to beat the previous world record of 66 lines: https://hallofdreams.org/posts/hatetris/