Developed a standards-compliant toggle feature for the Details element in the lightpanda-io/browser repository, focusing on enhancing user experience and accessibility. The implementation aligned with the HTML specification by enabling the open state of a parent Details element to toggle when its first Summary element is clicked. Leveraging HTML and Zig, the developer refined internal logic to ensure safe state transitions and prevent unintended behavior with non-first or orphan Summary elements. Comprehensive test coverage was added to validate open and close transitions, supporting a more predictable interaction model. The work emphasized front end development and robust testing practices throughout the process.