Despite ongoing curricular reforms, misconceptions in Newtonian mechanics remain widespread among lower secondary students and often persist after conventional instruction. Gravitas is a simulation-based learning game designed to identify and transform such misconceptions through a structured cycle of diagnostic tasks, cognitive conflict, and exploratory interaction. Grounded in Conceptual Change Theory, Self-Determination Theory, and Knowledge Space Theory, the game integrates misconception-oriented items, conflict-inducing animations, and non-evaluative, concept-focused feedback. Each level targets a specific misconception from the Force Concept Inventory and engages learners in a recursive cycle of prediction, conflict, feedback, and reconstruction. Event-level logging of responses, timing, and simulation use enables analysis of learning trajectories and strategies. By combining simulation-based learning with diagnostic logic, Gravitas provides a curriculum-aligned tool that supports conceptual change while generating research-grade data. This paper outlines the game’s theoretical foundations, instructional architecture, and motivational design, and discusses its potential as both a classroom-ready environment and a research platform for physics education.