I remember playing this in a browser. I'll try to find where.

edit: https://jimbly.github.io/regex-crossword/

oops there went my afternoon

I built a browser-based version that allows you to rotate it: http://www.stardrifter.org/regexp/

I've done this a few times over the years (and occasionally printed another copy when I made a mistake). Lots of fun. I wish there were more like it.