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