This session highlights the design process used to create The Evidence Game, an NSF-funded project to increase middle school science students’ thinking related to scientific argumentation including: understanding a claim, judging the evidence about a claim, determining the reasoning applied to the claim, considering rebuttals, and making judgments. The iterative design process includes input from both middle school teachers and students in the Kansas City Kansas School District. Recognizing that it may be difficult for middle school students to engage in scientific argumentation, we look at whether incorporating features such as focused goals, ease of learning, rapid and frequent responding, multi-player competitive play, various achievement levels, choice and autonomy, and increasingly challenging tasks, into the design will maintain student engagement.