This thesis is a collection of case studies involving small groups of physics students using so-called Controllable Worlds--i.e., a particular class of physics digital learning environment (DLE) including simulations, microworlds, and educational games that provides users with control over manipulable virtual environments. Several perspectives ranging from embodied cognition to semi-formalisms are employed and developed for the interpretation, analysis, and instructional guidance of physics students' engagement with DLEs. While this work focuses in particular on participants' use of two DLEs--namely, the 2D Newtonian software Algodoo and the PhET simulation My Solar System--it also contributes to the general scholarly discussion on student interaction and technology use in physics education. One such contribution, which relates to the development of an overarching taxonomy for learning environments in physics, is the theoretical distinction between 'constrained' and 'less-constrained' DLEs and between DLEs with high and low degrees of 'semi-formality.' Especially as compared to PER work that aims to measure learning gains or conceptual mastery via assessment tools, this thesis focuses instead on the mechanisms of meaning-making that occur between the 'pre' and 'post.' Thus, the theoretical picture of students' meaning-making in digitally-rich physics learning environments is further nuanced. Across all of the studies in this thesis, it is shown how the use of technology like Controllable Worlds can lead to student behavior which is productive for physics teaching and learning in ways that may be altogether unexpected.