Nowadays, computer, tablets, and mobile phones are part of everyday life. This leads to an integration of ICT into schools and into curricula. Especially mobile devices are offering new possibilities for kindergarten education. The digital learning environment MaiKe has been developed to foster mathematical competencies in kindergarten. The research study EfEKt evaluates the effects of MaiKe use in different settings. First results of the pilot study are illustrated by insights into two case studies outlining the effects of the digital features offered by the app MaiKe on habits and competencies performed.