Contributed to the ONSdigital/design-system repository by delivering three accessibility and usability enhancements focused on mobile navigation, text readability, and chart accessibility. Refactored the header navigation using CSS flexbox and JavaScript to create a responsive, expanded menu for small screens, improving both mobile usability and keyboard accessibility. Updated UI text highlight styles by removing background images and ensuring accessible underlining, enhancing readability for all users. Enhanced chart annotation accessibility by integrating detailed screen reader descriptions for points, ranges, and reference lines directly into the chart configuration. Work demonstrated a strong emphasis on accessibility, responsive design, and inclusive front end development practices.