I think I found this when I was reading a tutorial on JIT compilers: http://blog.reverberate.org/2012/12/hello-jit-world-joy-of-s...

Which I found in a simpler tutorial: http://nickdesaulniers.github.io/blog/2013/04/03/basic-jit/

TLDR;

It describes a programming competition/challenge that involves building programs in a self-contained VM that is built on its own programming language and system, meant to have been "discovered" as an ancient computing platform from thousands of years ago :)

The 2007 ICFP-PC was similar (in that you got a big opaque data file and the spec of a VM for it) and also very enjoyable. I was on the team that came second and I think we understand only about half of what was in there during the competition.

An oldie but a goodie. Unbelievably good playground for playing with functional languages. I had so much fun doing a bad job solving the optimization challenges.

But don't let the "functional" part scare you off -- you can do this in any language from assembly on up.

This is a pretty epic programming puzzle. Closest thing I can think of is Eric Wastl's Synacor Challenge.

The final puzzle in Synacor was BRUTAL, but overall, such a fun experience.

Unix shell programming: cult of the unbound variable.