Designing for Participation (DFP) is a design model for obtaining diverse learning outcomes in innovative learning environments. It fosters participation in social interaction that ensures individual understanding and overall achievement. DFP emerged from assessment-oriented design studies in several environments, including the Quest Atlantis 3D virtual environment. These refinements focused on an ecological science game called Taiga for grades 4-6. This chapter introduces the five general design principles that make up DFP, along with the more specific design principles that emerged across the Taiga refinement cycles. Specific game features are summarized, along with evidence of the impact of those features in the Taiga design studies.