Istiono, Wirawan. “Leveling up Difficulty Model Based on User Experience in Education Games Mobile-Based for Student Kindergartens”. IJNMT (International Journal of New Media Technology) 7, no. 1 (July 2, 2020): 18-22. Accessed April 19, 2024. https://ejournals.umn.ac.id/index.php/IJNMT/article/view/1666.