There is an Instructable for making one yourself https://www.instructables.com/CARDIAC-CARDboard-Illustrative...

My first computer. Inspired me to becomes a computer scientist when I was 10, in the early 1970s. I still have mine but the accumulator is burned out after too many write/erase cycles and I may have lost the "bug" (memory pointer). It's probably the only computer I have from last century that still works.

Me too! My mother sent me to an enriched program on Saturdays, and one of the “classes” they had was called “Queries and Theories” after a very interesting game.

That class introduced me to Mathematical Recreations, Raymond Smullyan, and computing. We had a CARDIAC we played with, and later went to the University to write FORTRAN programs on punch cards.

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):

https://news.ycombinator.com/item?id=4416054

Here's all I could find:

CARDIAC simulator in JavaScript (2014) https://news.ycombinator.com/item?id=8348615

CARDIAC (2014) https://news.ycombinator.com/item?id=8439443

Cardiac – A cardboard illustrative aid to computation (Bell Labs 1968) (2018) https://news.ycombinator.com/item?id=18433504

Cardiac: Portable cardboard computer (2016) https://news.ycombinator.com/item?id=12949393

Thanks! I've added https://news.ycombinator.com/item?id=8348615 to my comment above since it has comments.

The dale miller domain for the link (dang) above is down.

This is delightful. The paper sliders are especially charming.

I wonder if the tactility of it helped make assembly easier to learn - or harder, because it didn't have immediate feedback.

It was a match that burned twice. First, you could play with the cardboard computer then you could use it as a prototype to make a software version. In my case it was a gateway into 370 compatible assembler on an rca/univac.