Cave Generation in 21w07a

The large/huge caves that generate in 21w07a seem to generate way too rarely; the caves in 21w06a were a bit too huge and common, but it seems in this newer snapshot that they are incredibly rare and seem to be much smaller than they were before. I feel as if cave generation that is about halfway between 21w07a and 21w06a would strike a good balance between the two!

Also, pre-1.17 caves do not seem to generate past y=0, as they all seem to stop abruptly right before the y turns negative. 

The texture for grimstone could also be a little less busy and could generate slightly lower, but I do like the atmosphere it brings to the deep dark!