The WeWatt bike serves as an energy station that enables passers-by to charge their mobile devices through physical activity. However, despite multiple people using it simultaneously, the bike is typically used individually. To address this limitation, we developed the WeWattTree, an installation utilising human-powered energy to filter environmental air. Through the orchestration of subtle motion gestures, our goal is to entice passers-by to participate and encourage them to socially interact, synchronising their pace. In this work-in-progress, we provide insights into the prototyping process, combining physical experimentation and computational simulation, and delve into the underlying concepts of our grammar of motion gestures. We highlight how a single design effectively merged multiple functionalities, how the role of material characteristics shaped the interaction design, and discuss the potential for social performances as captivating public displays.