Responsive or active shading devices feature various designs that enable automated adjustments to enhance performance in environmental conditioning. However, existing solutions mostly yield high cost and demand complex installation while featuring minimal support for convenient customization. Pneumactive is a prototypical exploration of the performance, usability, and aesthetics of pneumatic actuator and membrane assemblies toward soft, modular, affordable, and customizable responsive shading device designs. The transformable system is achieved by programming the internal structures (strain limiters) of each actuator and compositions of actuators and membranes suspended among them. An automated control system was designed to enable not only explorations of the morphological behavior of the device with each component independently actuated to various levels, but also an opportunity to experiment with interactive programs based on a set of parameters including time intervals, light intensity, and distance to moving objects. The thesis will demonstrate the iterative development process in actuator design, material testing, fabrication technique, and interaction study. The final prototype attempts to provide implications of the feasibility and usability for shading applications through a series of testing on a fully integrated device system. This research will shed light on the potential applications of soft robotics in architecture while advancing concepts in material, fabrication, interaction study, and design for usability in the development of responsive architectural devices.