Dwarf Fortress is one of those oddball passion projects that’s broken into Internet consciousness. It’s a free game where you play either an adventurer or a fortress full of dwarves in a randomly generated fantasy world. The simulation runs deep, with new games creating multiple civilizations with histories, mythologies, and artifacts. I reached out to him to see how he’s managed a single, growing codebase over 15+ years, the perils of pathing, and debugging dead cats. Our conversation below has been edited for clarity.