When Derek Yu released Spelunky for free in 2008, his roguelike-inspired platformer took the indie game community by storm with its combination of classic platform mechanics, extreme difficulty, and random level generation. Four years later, Spelunky's HD remake went on to become PC Gamer's Game of the Year and earn perfect scores from Polygon and Eurogamer. But how is a "perfect" game made? Spelunky is Boss Fight's first autobiographical book: the story of a game's creation as told by its creator. Using his own game as a vehicle, Derek Yu discusses such wide-ranging topics as randomization, challenge, indifferent game worlds, player feedback, development team dynamics, and what's required to actually finish a game. Grab some ropes, a mattock, and your favorite pug—this book is going to dig deep.