Helping students reach a clear understanding of the cause-and-effect relationship between changes in parameter and the graph of an equation is the focus of the activity outlined in this article. The behavior of phase shifts has been regarded as counterintuitive for many people, and often, because of this, conflict between student intuition and teacher instruction arises in the classroom (Zazkis et al., 2003). Math action technology can be used to position students as mathematical explorers and empower them to develop a greater sense of agency (McCulloch et al., 2021). In this lesson, the authors used Desmos's Activity Builder to help students discover, arrive at, and understand the "why" of the phase shift concept.