Curved Side Spaces (BRSL) in learning need to be presented with learning media to make it easier for students to understand the concept. This research aims to produce learning media based on technology and cultural values. The media in question is (BRUSLE) an Android application that can be accessed via mobile with augmented reality hologram content and integrated traditional Engklek game in the learning process. Development research was conducted using the ADDIE model (Analysis, Design, Development, Implementation, Evaluation). The development was carried out based on a needs analysis at grade 7 in 2023 Mathematics Subjects on BRSL material. The developed product was carried out content validity by 3 experts (media, mathematics learning, and practitioners/teachers) to continue the feasibility test. The class used in this study is class 7D based on the teacher's recommendation. The trial was carried out data collection techniques were carried out with a pretest-posttest to measure students' understanding of the material. The use of questionnaires and documentation in research to find out the response of students to the use of BRUSLE and record all learning activities. Statistical data testing was carried out using the Paired Sample T Test to prove that the use of BRUSLE proved to have a significant difference. The results showed that there was a significant difference of 0.001 < 0.05 which indicated that BRUSLE by Engklek Ethno-Games media was effective in improving understanding of mathematical concepts.