Last April OpenStreetMap got a new open-source editor: MAPS.ME. It was a first popular editing application both for iOS and Android phones, with millions of users. Suddenly a quarter of daily editors were maps.me users, who behaved quite differently from regular, hardcore mappers. This talk explains how we made editing OpenStreetMap possible offline, without an access to the constantly updating database, how we and our users repeatedly broke OSM data, and which tools and algorithms there are for fixing the map.