Some of the world's most popular games—Counter-Strike, Dota, PUBG—started not as commercial products, but as "mods" created by amateurs for free. In "Built by Fans," tech writer Elliott Ray explores the fascinating symbiotic (and often parasitic) relationship between game developers and the modding community. Ray details how unpaid fans often fix bugs, restore cut content, and improve graphics years before the official developers bother to. He highlights the tension of "unpaid labor": Are modders hobbyists expressing love, or are they exploited workers increasing the value of a product they don't own? The book covers the legal battles over intellectual property, the rise of "paid mods," and the democratizing power of tools that allow anyone to rewrite the rules of a virtual world. It is a tribute to the coders, artists, and tinkerers who refuse to accept the game as it was sold, proving that the player sometimes knows better than the creator.