During February 2026, Malu Cartwright developed the Dark Castle theme for the zed-industries/extensions repository, focusing on enhancing the application's user interface for low-light environments. The work centered on theme development and UI/UX design, utilizing TOML to define a dark yet colorful palette that balanced visual appeal with accessibility. Collaborating with Finn Evers, Malu ensured the theme improved readability through a high-contrast color scheme, directly addressing user needs for flexible and user-friendly theming options. While the contribution was limited to a single feature, the implementation demonstrated a thoughtful approach to UI theming and laid groundwork for future extensibility.