Developed in Hocheon Village, a dense hillside neighborhood in Busan, ECO ART: Planting the Stars began from the rooftop as both a symptom and a surface of urban heat. Over 43 days, approximately 500 residents and volunteers brought cool-roof action to 97 rooftops, reducing heat while transforming the neighborhood into a shared visual field. The project connected ecological action, neighborhood stories, and live climate data through three linked works, including Moonlight, a solar-powered media installation whose color shifted in real time through rooftop temperature data. By weaving environmental response, media, and local participation together, the project proposed a form of public art rooted in everyday community life.