Background/purpose: Several previous studies have attempted to develop Android learning media for elementary students beginning to learn counting. However, no media with a levelled adventure theme exists. The purpose of this research is to develop an android-based learning media, B'Math, to improve elementary students' counting skills. Materials/methods: This type of research is research and development using the ADDIE model: 1) Analyze, 2) Design, 3) Development, 4) Implementation, and 5) Evaluation. B'Math is an Android-based learning media-themed adventure game with levelled counting material, including number symbols, comparing, matching, addition, and subtraction, the results of which come to less than 20. The research subjects were 184 grade one students from two elementary schools in Indonesia. Data collection techniques included observation, interviews, and tests. Data analysis was conducted using descriptive and inferential statistical methods. Results: This research successfully developed B'Math, an Android-based learning media designed to improve the early calculation skills of elementary school students. The results of this study showed that the learning outcomes of students who learnt using B'Math were higher than those of students who learnt using conventional learning approaches. This proves that the B'Math learning media have been effective in enhancing students' initial counting skills at the elementary school level. Conclusion: The study's results illustrate a need to develop learning media to improve elementary school students' initial counting skills.