One past thread:
CARDIAC simulator in JavaScript - https://news.ycombinator.com/item?id=8348615 - Sept 2014 (5 comments - thanks miles)
CARDIAC Cardboard Computer Emulator - https://news.ycombinator.com/item?id=641032 - June 2009 (5 comments)
Tangentially related:
PAPAC-00, a Do-It-Yourself Paper Computer (1958) - https://news.ycombinator.com/item?id=15026101 - Aug 2017 (12 comments)
I think there have been others...anyone?
Edit: A fun comment from a different thread (Aug 2012):