<![CDATA[Background: Curved surface geometry is often difficult for junior high school students because the concepts require strong spatial visualization skills. Augmented Reality (AR) offers opportunities to support mathematics learning through interactive three-dimensional representations.Aims: To facilitate the learning of curved surface geometry, a mobile-based Augmented Reality (AR) application was designed and implemented. Its feasibility and effectiveness were then examined to determine its contribution to improving students' mathematics achievement.Methods: A research and development (R&D) approach based on the ADDIE model was adopted in this study. The application incorporates three-dimensional geometry visualization, object interaction, learning content, quizzes, and final assessments. Its feasibility was assessed by experts in materials, media, and instructional design. A post-test-only quasi-experimental design was used to investigate its effectiveness, involving 30 students in the experimental group and 30 students in the control group. The collected data were analyzed through descriptive statistics and an independent samples t-test.Results: With a feasibility score of 88.42%, the application was categorized as very feasible and obtained a practicality rating of 90.20% from students. Students in the experimental group achieved a higher average post-test score (M = 13.57, SD = 1.16) compared with those in the control group (M = 12.37, SD = 1.38). The independent samples t-test indicated a statistically significant difference (t = 2.165, p < .05), demonstrating better learning performance among AR application users.Conclusion: The developed AR application was feasible for classroom use and was associated with improved mathematics learning outcomes in curved surface geometry. Further studies involving larger samples and broader learning indicators are recommended.]]>
