The design tool that defined the pre-Figma era. Mac-only, file-based, and dramatically better than Photoshop for UI work when it launched in 2010. Sketch's eventual displacement by Figma (browser-based, multiplayer, cross-platform) is a clean case study in how a better-for-today tool can get replaced by one built for the next era. A cautionary tale for anyone designing for current-workflow instead of next-workflow.