Over a three-month period, Heap successfully revamped the design of its web application to create a more modern and consistent user interface without disrupting existing workflows or introducing major bugs. This was achieved through a meticulous and incremental approach, where the design updates were continuously shipped to production using feature flagging, which allowed for early and frequent validation in the production environment. The project focused primarily on changes to stylesheets rather than markup or behavior, employing techniques such as branching CSS selectors and extracting CSS custom properties to handle specificity challenges. Additionally, Heap replaced its in-app icon set with more cohesive icons, using a placeholder icon to identify and eliminate inconsistencies. The gradual rollout of the visual refresh included internal testing and a beta release to a customer cohort, allowing for feedback and adjustments prior to the full release. This strategic approach minimized risks and maintained ongoing feature development, showcasing the importance of careful planning and incremental deployment in large-scale design projects.