Findings synthesized across five empirical, laboratory-and classroom-based studies of high school and college students engaged in geometric reasoning and proof production during single and multi-session investigations (346 participants overall) are presented. The findings converge on several design principles for embodied mathematical thinking and learning. "The Hidden Village" is presented as an instance of an embodied learning environment that uses the narrative context of a visual novel to instantiate these design principles and investigate their influences on mathematical thinking and learning, and to inform a broader theoretical framework of grounded and embodied learning. The interplay of theoretical, empirical, and design considerations of grounded and embodied learning reframes learning, transfer, and assessment, offering promising new pathways for an emerging class of learning environments. Grounded and embodied learning Grounded and embodied learning (GEL) offers a framework for understanding and designing for meaning making based on body-based processes. These GEL processes include actions, gestures, operative speech, and collaborative movements, as well as processes for supporting simulated action and imagination. Evidence is mounting that GEL is also activated during interventions, such as when learners are prompted to perform directed actions or are prompted to engage in simulated actions. This paper summarizes a set of interwoven empirical, theoretical, and design advancements for mathematical reasoning and their implications for teaching, learning, learning environment design, and assessment. The theoretical contributions offer hypothesis-driven inquiry into the nature of learning and meaning making through body-based experiences, and principled guidance for the design of learning technology and educational experiences. Empirical contributions span several laboratory-and classroom-based studies of high school and college students and high school teachers; in all, some 346 participants who engaged in 5 single and multi-session investigations. These investigations provide evidence of the role of embodied processes for meaning making in support of mathematical reasoning and theoretically guided design principles to promote learning. Design advancements to technologies for embodied thinking and learning serve as essential instantiations of theoretically derived hypotheses, as well as vital spaces in which embodied behaviors are elicited and data collected. Empirical findings and theoretical progress inform improvements in learning environment design that then make possible further theoretical and empirical advancements. In the final section, we explore how the interplay of evidence, theory, and design offer pathways for progress on complex issues facing GEL, such as generalizing research, bridging research and practice, and the emergence of designs and design principles. [This paper was published in: "ICLS Proceedings," International Society of the Learning Sciences, 2022, pp. 179-186.]