This free-access report by the PhET simulation team discusses foundations of tool-mediated learning, tool design, and human computer interaction to develop a framework for implicit scaffolding in learning environments. In education, scaffolding is a way for teachers to provide support while students master new concepts and skills. In simulation design, implicit scaffolding means providing feedback to frame and scaffold student exploration without explicit guidance. It is considered a particularly useful design framework for interactive simulations in science and mathematics. A key purpose of implicit scaffolding is to support a range of educational goals including affect, content, and scientific reasoning processes. In particular, the use of implicit scaffolding creates learning environments that are productive for content learning and are able to simultaneously support the affective goals of student agency and ownership over the learning process - goals that may not be addressed in more directed learning environments. This report describes how the framework is applied in the context of the Energy Skate Park: Basics simulation, a simulation aimed at middle school student learning of energy concepts. Interview data provides an examples of how teachers might use implicit scaffolding in the classroom.