This study aims to understand a middle school mathematics teacher's instruction and reflections on her experiences with supplementary curricular materials enriched with interactive simulations--PhET interactive simulations (sims) and sim-based materials--over two years. We conceptualize Linda's (pseudonym) teaching in terms of both thinking and doing. Regarding Linda as doer, results show significant differences in Linda's instruction, favoring sim lessons compared to non-sim lessons. Regarding Linda as thinker, results show increased attention to problems of practice related to teaching, as well as more productive framing of problems of practice. When these two findings are taken together, shifts in what Linda did and thought illustrate the potential for high-quality supplementary materials to function as a catalyst for change as we map the flow of shifts in what Linda thought and did across two years. [For the complete proceedings, see ED630210.]