CSSi

CSSi is a hypothetical modular styling system designed to extend and optimize CSS workflows. It introduces a component-scoped style graph and a build step that compiles to standard CSS, enabling maintainable design systems, tokens, and theming.

History: First proposed in online discussions in the early 2020s as an approach to address CSS scalability; several experimental projects exist; there is no formal standard.

Architecture: The system comprises a CSSi input language, which resembles CSS but permits components, tokens, and conditional rules; a style graph that captures dependencies and inheritance; and a compiler/runtime that outputs normal CSS and applies runtime themes. It supports design tokens, themeable variables, and scoping rules to prevent style leakage.

Usage: Teams adopt CSSi to manage large-scale design systems and consistent theming across apps; it integrates with build pipelines and modern frameworks; migration can be incremental using adapters.

Reception: As of now, CSSi remains experimental with limited tooling and documentation; advocates cite improved maintainability, while critics point to increased complexity and potential vendor lock-in.