Sumi.css is a minimalist, classless-first CSS framework. Write plain, semantic HTML and it looks finished. Add a class only when you want something specific. The framework ships as one file with no build step, measuring 6.7 KB minified and gzipped, with no JavaScript and no dependencies.
Classless by default, Sumi styles headings, forms, tables, cards, accordions, modals and navigation directly from the HTML element alone. It supports light and dark mode, following the visitor's system setting automatically, while data-theme lets developers force either mode.
Theming is straightforward. Every color, font, size and radius is a CSS custom property. Element styles carry zero specificity, so your own CSS always wins without !important.
Accessibility is built in, with visible focus rings, ARIA-driven states such as aria-invalid, aria-busy and aria-current, and support for reduced motion. Developers can install Sumi by copying sumi.min.css into a project or loading it from the repository through jsDelivr. The unminified sumi.css is available during development, with comments explaining each section.
Source: Hacker News · Summarized by HeadlinesBriefing