The chapter explores the use of map editors and level designers in game development, focusing on the tools used for Celeste and their upcoming game Earthblade. It discusses the importance of speedrunning in game development, reflecting on its influence on Celeste and how it will be incorporated into Earthblade. The chapter also delves into the challenges of deciding on the right tools for game development, shares insights on creating custom physics engines, and provides tips for indie developers and small teams.