This design case discusses the complex collaborative design reasoning processes involved in developing an online interactive learning tool for learners of all ages to explore and understand the role of flagellate plants in our society. The learning tool consists of a main website (the "Voyager") and an interactive, dynamic map of the evolutionary relationships between thousands of flagellate plant species (the customized "OneZoom" web application). The design and development of this innovative learning tool required expertise in collaborative design, design reasoning, project management, theories of learning and instructional strategies, software development, and web usability. Collaboration platforms used by the project team involved "GitHub" and "Slack." Domain knowledge needed to complete the project included botany (flagellate plants), web programming ("Python" and "JavaScript"), and database management ("MySQL"). The project included a team of international experts who negotiated design strategies and solutions over the course of a year and produced and improved prototypes until converging on the final product. This article explains the challenges faced during these processes and presents solutions and lessons learned from this experience.