Finally got around to hacking up my own mod for factorio a month or so ago (bigger cargo wagons). As with the rest of their work, the "how to make a mod" process and documentation is exemplary. There's accurate documentation for everything, pretty much, provided by the developers, and kept up to date.

Contrasted with other games where "the community" and developers request docs and examples be taken down if someone tries to publish such; it's all the more wonderful.