CSS-First Agent Skill

Transform any AI agent into a CSS-first expert. Zero-JavaScript solutions using cutting-edge CSS features (2021-2026).

What It Does

This skill gives AI agents deep knowledge of modern CSS so they provide CSS-only solutions instead of reaching for JavaScript. It includes:

• 7 behavioral rules — CSS-only enforcement, logical properties, modern features, semantic intent analysis, framework detection, browser support, progressive enhancement
• 57 production-ready CSS demos — layout, responsive, container queries, animation, theming, positioning, interaction, visual, specificity, functions & values
• Live MDN integration — fetch current Baseline status and browser support data on demand

Features

Capability	Description
Semantic Intent Recognition	Detects layout, animation, spacing, responsive, visual, and interaction intents
Framework Detection	Auto-detects React, Vue, Angular, Svelte, Tailwind, Bootstrap
Logical Properties First	Prioritizes inline-size, margin-inline, etc. for internationalization
Modern CSS (2021-2026)	Container queries (incl. name-only), view transitions, scroll-driven/triggered animations, light-dark(), anchor positioning, @layer, @scope, revert-rule, if(), @function, advanced attr(), contrast-color(), grid lanes, gap decorations, shape-outside shapes
Browser Support Awareness	Every suggestion includes Baseline status (Widely Available / Newly Available / Limited / Experimental)
Progressive Enhancement	Core functionality first, enhancements layered with @supports

Quick Reference

Status	User Intent	CSS Solution	Demo
🟢	Center element	Flexbox / Grid	css-demos/layout/centering-logical.css
🟢	Aligned grids	Subgrid	css-demos/layout/subgrid.css
🔵	Parent selection	:has()	css-demos/layout/has-selector.css
🔵	Component styles	CSS Nesting	css-demos/layout/css-nesting.css
🟣	Masonry layout	Grid Lanes	css-demos/layout/grid-lanes-masonry.css
🟢	Responsive layout	Media queries (range syntax)	css-demos/responsive/media-queries.css
🟢	Feature detection	@supports	css-demos/responsive/supports-rule.css
🟢	Container responsive	Container size queries	css-demos/container/size-queries.css
🟡	Component theming	Container style queries	css-demos/container/style-queries.css
🟣	Sticky detection	Scroll state queries	css-demos/container/scroll-state-queries.css
🟣	Tooltip arrow flip	Anchored container queries	css-demos/container/anchored-queries.css
🟣	Container by name	@container name without type	css-demos/container/named-queries.css
🔵	Dark mode	light-dark()	css-demos/theming/light-dark-function.css
🔵	Page transitions	View Transitions (+ element-scoped)	css-demos/animation/view-transitions.css
🟡	Scroll effects	Scroll-driven animations	css-demos/animation/scroll-driven.css
🟣	Scroll reveals	Scroll-triggered animations	css-demos/animation/scroll-triggered.css
🔵	Entry/exit animation	@starting-style	css-demos/animation/starting-style.css
🟡	Tooltips	Anchor Positioning	css-demos/positioning/anchor-positioning.css
🟣	Carousel / Tabs	CSS Carousel	css-demos/interaction/css-carousel.css
🔵	Popovers / Dropdowns	Popover API	css-demos/interaction/popover.css
🟢	Touch vs pointer	Hover media queries	css-demos/interaction/hover-media-queries.css
🟢	Form validation	:user-valid / :user-invalid	css-demos/visual/form-validation.css
🟢	Color variations	color-mix()	css-demos/visual/color-mix.css
🟣	Modern shapes	corner-shape	css-demos/visual/corner-shape.css
🟣	Text wrap around shapes	shape-outside shape functions	css-demos/visual/shape-outside-functions.css
🔵	Underline ink skipping	text-decoration-skip-ink	css-demos/visual/text-decoration-skip-ink.css
🔵	Crisp pixel-art scaling	image-rendering: crisp-edges	css-demos/visual/image-rendering.css
🟢	Aligned / steady digits	font-variant-numeric: tabular-nums	css-demos/visual/font-variant-numeric.css
🟣	Conditional values	if()	css-demos/functions/css-if-function.css
🟣	Reusable logic	@function	css-demos/functions/custom-functions.css
🟣	Data-driven styles	Advanced attr()	css-demos/functions/advanced-attr.css
🔵	Auto contrast text	contrast-color()	css-demos/functions/contrast-color.css
🟢	Cascade control	@layer	css-demos/specificity/cascade-layers.css
🔵	Scoped styles	@scope	css-demos/specificity/scope-rule.css
🟣	Roll back one rule	revert-rule	css-demos/specificity/revert-rule.css

Structure

SKILL.md                          # Skill definition (loaded by agents)
references/
  rules/                          # 7 behavioral rules
  live-mdn-fetch.md               # Live MDN data fetch workflow
css-demos/
  INDEX.md                        # Full catalog with MDN links & baseline status
  layout/                         # Centering, spacing, subgrid, :has(), nesting, grid lanes
  responsive/                     # Media queries (range syntax), @supports
  container/                      # Size, style, scroll-state, anchored, name-only queries
  animation/                      # View transitions, scroll-driven, scroll-triggered, @starting-style
  theming/                        # Dark mode with light-dark()
  positioning/                    # Anchor positioning
  interaction/                    # CSS Carousel, popover, hover media queries
  visual/                         # Form validation, color-mix(), corner-shape
  functions/                      # if(), @function, advanced attr(), contrast-color()
  specificity/                    # @layer cascade layers, @scope scoped styles

Baseline Status Indicators

• 🟢 Widely Available (95%+) — safe for production
• 🔵 Newly Available (85-94%) — recently stable, verify target browsers
• 🟡 Limited Availability (70-84%) — use with progressive enhancement
• 🟣 Experimental (<70%) — cutting-edge, use cautiously

License

MIT