Built a reusable theming module, refactored and rewrote basically every view in the app to use it, and shipped Dynamic Type and Dark Mode support with semantic color and font mappings. Overhauled accessibility support to meet WCAG 2.1 level AA standards. Fixed numerous bugs, filed radars, all that jazz. Shipped features, mentored engineers, improved developer tooling and language standards, learned & evangelized RxSwift, helped define process.