This study develops a prototype of a batik-based geometric transformation e-module for junior secondary students. A limited research and development approach adopts ADDIE, with the present work covering analysis, design, development, and formative mathematical checking. Literature exported from two Scopus searches was screened by publication year, with all 2026 records excluded. Selected references were checked against Crossref and publisher metadata. Documented motifs inform learning contexts, while newly drawn geometric illustrations are explicitly distinguished from authentic cultural artifacts. The offline HTML prototype includes four transformation units, an interactive coordinate explorer, 12 feedback-supported questions, and eight open-response assessment items. Deterministic checks use a triangle with vertices (1,1), (4,1), and (2,3). Translation, reflection, and rotation preserve length and area; dilation with scale factor 2 produces length and area ratios of 2 and 4. These findings demonstrate internal mathematical consistency, rather than educational effectiveness. Expert validity, classroom practicality, and preliminary learning outcomes remain to be tested using the proposed instruments. The contribution is a traceable connection between documented batik contexts, mathematical abstraction, and digital learning activities, accompanied by an explicit separation of prototype evidence from future empirical evidence.