Ching-Yuan Ku is in the first year of studying a Master of Design in Swinburne University of Technology, specialises in communication design. The mobile app "Talk to Casey" is inspired by co-design course this semester. The City of Casey is currently facing an issue of population growth and sustainability will be a main goal for the city. Besides, multiple studies show that green space is a crucial element to maintain sustainability. The app aims to provide a platform for each stakeholder to share their ideas about green space in their neighbourhood. Ultimately, each stakeholder' opinion can be seen or adopted.