I just came back to check if anyone else was discussing their entry, so thanks for posting your write up!

I wrote mine by hand just testing it using the in-browser simulator. I initially used subroutines to try to keep things structured but then resorted to inlining most things (and flattening as much state as I could to bare registers) to try to speed things up, though i never quite got my ants to always move within the 64 op step.

My best score on the official test set was 654 (43rd place). I put my code and a little write up here: https://github.com/cristoper/brain.ant