Mark Damon Walker formalized pushout colimits in the agda/agda-categories repository, delivering a foundational feature for category theory tooling. He used Agda to construct rigorous formal proofs, applying advanced concepts from type theory and category theory to ensure mathematical correctness. This work addressed the need for reliable, formally verified colimit constructions, which are essential for building higher-level abstractions in categorical libraries. By strengthening the theoretical underpinnings of agda-categories, Mark’s contribution improved maintainability and provided a robust base for future extensions. The depth of his approach reflects a strong command of formal proofs and a careful attention to foundational mathematical detail.