This educational game on musical themes familiarises the players with the phenomenon of the glissando, and makes it possible to compose one’s own music pieces made up of glissandi. Glissando is a fluid transition between two sounds differing in pitch. While playing with the app, we can form glissandi in a simple, intuitive manner. We can freely determine their beginnings and ends, their inclination and durations in sound space. The app also makes it possible to superimpose glissandi on one another, create various sound configurations out of them and enjoy their unusual sound. The app has been conceived as a complement for the educational children’s book Glissando, which came out in the series Sonia in the Land of Sonoroos. The title heroine gets to know various sound phenomena through meetings with fabulous creatures from the land of sounds. The series includes, apart from Glissando, also two other booklets: Ostinato and Harmonics, each accompanied by a mobile app. We invite you to get acquainted with these publications.