The Friday Facts were fantastic. I don't know of any other non-open-source project (but counterexamples are of course welcome) that encourages the developers to put that much technical information about what they're up to out on the website. I especially loved the ones about belt optimizations, multi-threading, and the networking model, since those are all interesting problems that any game developer is likely to think about but not necessarily get around to really solving the way that Factorio did. The FFF's inspired me to, on a total lark, send over my resume, which turned out to be good timing.

I think my "holy crap I'm working on factorio, pinch me" was equivalent to some people's "holy crap I'm working for Microsoft." I still remember the odd smell of the office when I first walked in ("sorry it smells like acid in here", I was told, and was later disappointed to learn that when Europeans say "smells like acid" they just mean it smells bad; there was no open use of entheogens while I was there).

I'm glad fff-200 made the cut for this guy's list, as that's the one where I announced the new 'programmable noise' terrain generator. More deets in https://www.factorio.com/blog/post/fff-207, https://www.factorio.com/blog/post/fff-258, and https://www.factorio.com/blog/post/fff-282, among others.