The CASCADE-MUCH system was designed to help teacher-designers in Shanghai, China with the development of instructional scenarios for multimedia curricula. After four rounds of prototyping, a summative evaluation was carried out to assess practicality. Results showed that the system was practical for the intended target users in Shanghai and also had potential for users in other contexts. The purpose of this article is to present the design process of the CASCADE-MUCH program and discuss how the evolutionary prototyping approach improved program quality and contributed to the designer's knowledge growth.