I was really pleased with the vgrep technique he used at the start to figure out what changed the map data. I often forget just how awesome our eyes are at spotting changing stuff at a glance and small datasets don't take long to manually look at.

Simply open the working RAM and look at it; lo and behold the thing is right there.

(There's some super spiffy things built on this idea, the one I was really excited to see come out was ..cantor.dust.. [0], which was never released.)

[0] https://sites.google.com/site/xxcantorxdustxx/

EDIT: formatting