# `PhiaUi.ThemeCSS` [🔗](https://github.com/charlenopires/PhiaUI/blob/v0.1.17/lib/phia_ui/theme_css.ex#L1) Generates CSS custom property declarations from a `%PhiaUi.Theme{}` struct. This module is responsible for converting PhiaUI theme data into valid CSS strings. It supports three output modes that cover the most common scenarios: ## 1. Root-scoped CSS (single active theme) Use `generate/2` when you want one theme to apply globally to your application. The output uses `:root` and `.dark` selectors. theme = PhiaUi.Theme.get!(:blue) css = PhiaUi.ThemeCSS.generate(theme) # => "/* PhiaUI Theme: Blue */\n@theme { ... }\n:root { ... }\n.dark { ... }" Inject the output as a `