This mixed-method study aims to explore the feasibility of using the game-based, multimodal representation of mathematical problems to support middle school students' practice and performance of math problem representation and solving. A three-dimensional architectural simulation game, called E-Rebuild, was developed to engage students in architecture-themed math problem solving and learning. Based on the data collected from 56 middle graders, the study findings suggested that interacting with game-based multimodal math problems helped students develop a systematic perspective and an analytical demeanor in coordinating external problem representations distributed across game objects and actions. Game-based problem solving promoted participants' mathematical test performance as well as mental rotation task performance.