This design case details the ten-year (2014-present) iterative process to design and develop a graph-based computer-assisted program to support middle school students' development of collaborative argumentation. We begin by describing the first two iterations of the design and discuss how we learned from the process failures. This paper focuses on the most recent iteration of the graph-based computer-assisted program that has evolved to incorporate the multiplayer function to support the representation of collaborative scientific argumentation for middle school students. The students' and teacher's experiences using the multiplayer game-based computer-assisted program are documented.