[piebro]

https://github.com/R-O-C-K-E-T/Factorio-SAT is another codebase trying to tackle the same problem

[progbits]

This is the one from which most balancer books are made and if I recall correctly the first one that made SAT work for this problem.

[moomin]

The 4x4 with a 90 degree turn is a thing of beauty.