hexo-theme-butterfly is a feature-rich, card-based UI theme for the Hexo static site generator. It is not a standalone application but a theme package that integrates deeply with Hexo's extension APIs: Pug templates for layouts, Stylus stylesheets for the visual system, vanilla JavaScript for client-side interactions, and Node.js scripts that register tag plugins, helpers, filters, and event handlers to enrich content generation. Its production role is to transform raw Markdown posts and site configuration into a polished, interactive blog front-end complete with comments, search, analytics, dark mode, Pjax navigation, code syntax highlighting, and various content widgets such as tags, archives, series, and related posts. The architecture is configuration-driven, with a large default config object that users can override, and it relies on a centralized asset manifest (plugins.yml) to load third-party CSS/JS from CDNs. It also supports multi-language i18n through YAML language files and provides numerous optional integrations (Disqus, Gitalk, Waline, Twikoo, Algolia, Google Analytics, etc.) behind conditional Pug includes. While the repository is a theme, it demonstrates reusable engineering patterns in its utility libraries, CSS mixins, and Hexo plugin design, making it useful as a reference for static-site theme development. There are no data science or research components; this is purely an application/theme repository.