The course of digital filter design in electronics/electrical engineering involves complicated mathematical equations and dynamic waveform variations. It is a consensus among educators that using simulation tools helps improve students' learning experience. Previous studies on system simulation seemed to lack an appropriate approach to design such a course. Few emphasized the design of an interactive learning environment by using an evolutionary approach. This study integrated the design concept of an evolutionary approach and Web service-based technology into a simulation system entitled PEWSILE (Pedagogical Web Service-based Interactive Learning Environment) was introduced. The PEWSILE system contained two interactive learning environments-a simple system and an advanced system. It offered a total of six pedagogical Web services. The simple interactive learning environment included text/color-based service, and text/color/diagram-based service. The advanced interactive learning environment included batch-based, interval change-based, comparison-based, and scroll bar-based services. In sum, this study provides helpful and meaningful implications in designing educational software.