<![CDATA[Mathematics teaching on the topic of flat-sided three-dimensional shapes is still dominated by the use of printed worksheets, which are not very interactive and do not optimally encourage students to discover concepts independently. Furthermore, the use of local culture as a context for mathematics learning remains limited. This study aims to develop an Electronic Student Worksheet (E-LKPD) for flat-sided shapes based on discovery learning with a Kasongan cultural context that meets the criteria of validity, practicality, and effectiveness This study uses the ADDIE development model. The research subjects comprised two mathematics education lecturers, one mathematics teacher, and 32 students in Class VIII-A at a school in Bantul. Data were collected through interviews, validation sheets, response questionnaires, and problem-solving ability tests, then analysed both qualitatively and quantitatively. The results of the study indicate that the E-LKPD developed meets the criteria of validity, practicality and effectiveness. The validity of the E-LKPD was demonstrated by an average validation score of 102.33, categorised as very good. Its practicality was demonstrated by an ideal percentage of 93.33% among teachers and 76.41% among students. Effectiveness was demonstrated by the results of the paired sample t-test, with a significance value of 0.000 < 0.05, indicating a significant difference between the pre-test and post-test scores. Consequently, the E-LKPD developed is suitable for use in mathematics teaching.]]>
