stacks-crosswind

name	stacks-crosswind
description	Use when styling components in a Stacks application — utility-first CSS classes, theming, responsive design, variants, custom rules, or CSS generation. Crosswind is the CSS utility engine powering Stacks' Crosswind config.
license	MIT
compatibility	Bun >= 1.3.0, TypeScript
allowed-tools	Read Edit Write Bash Grep Glob

Crosswind CSS Framework

Crosswind (@cwcss/crosswind) is the utility-first CSS engine for Stacks — similar to Tailwind CSS but built for Bun.

Design & anti-slop skills

For taste-level guidance on which utilities to reach for (layout variance, spacing rhythm, color calibration, motion), see the design-taste family: stacks-design-taste (flagship), the presets stacks-design-soft / stacks-design-minimalist / stacks-design-brutalist, stacks-redesign, stacks-design-output, and the image-first stacks-image-to-code / stacks-imagegen-web / stacks-imagegen-mobile / stacks-brandkit.

Key Paths

• Package: node_modules/@cwcss/crosswind/
• UI config: config/ui.ts (Crosswind options referencing Crosswind)
• Default styles: storage/framework/defaults/styles/
• Output: storage/framework/stx/cache/cw-<hash>.css, one file per page (stx's stateDir, set in config/ui.ts)

Core API

CSSGenerator

import { CSSGenerator } from '@cwcss/crosswind'

const generator = new CSSGenerator(config: CrosswindConfig)
generator.generate(className: string): void    // Process a single class
generator.toCSS(includePreflight?, minify?): string  // Output CSS
generator.reset(): void                        // Clear generated CSS

Parser

import { parseClass, expandBracketSyntax, extractClasses, extractAttributifyClasses } from '@cwcss/crosswind'

parseClass('hover:bg-blue-500'): ParsedClass
// { raw: 'hover:bg-blue-500', variants: ['hover'], utility: 'bg-blue-500', important: false, arbitrary: false }

extractClasses(htmlContent: string, options?): Set<string>
expandBracketSyntax('text-[#1a1a1a]', config?): string[]
extractAttributifyClasses(content, config?): Set<string>

Scanner

import { Scanner } from '@cwcss/crosswind'

const scanner = new Scanner(patterns: string[], transformer?, extractOptions?)
await scanner.scan(): Promise<ScanResult>
await scanner.scanFile(filePath: string): Promise<Set<string>>
scanner.scanContent(content: string): Set<string>

Build Functions

import { build, writeCSS, buildAndWrite } from '@cwcss/crosswind'

const result = await build(config: CrosswindConfig): Promise<BuildResult>
await writeCSS(css: string, outputPath: string): Promise<void>
await buildAndWrite(config: CrosswindConfig): Promise<BuildResult>

interface BuildResult {
  css: string
  classes: Set<string>
  duration: number
  compiledClasses?: Map<string, { className: string, utilities: string[] }>
  transformedFiles?: Map<string, string>
}

Bun Plugin

import { plugin } from '@cwcss/crosswind'

const bunPlugin = plugin(options?: CrosswindPluginOptions): BunPlugin

Configuration

interface CrosswindConfig {
  content: string[]                    // Glob patterns for source files
  output: string                       // Output CSS file path
  minify: boolean
  watch: boolean
  verbose?: boolean
  theme: Theme
  shortcuts: Record<string, string | string[]>
  rules: CustomRule[]
  variants: VariantConfig
  safelist: string[]                   // Always include these classes
  blocklist: string[]                  // Never include these classes
  preflights: Preflight[]
  presets: Preset[]
  compileClass?: CompileClassConfig
  attributify?: AttributifyConfig
  bracketSyntax?: BracketSyntaxConfig
  cssVariables?: boolean
}

Theme

interface Theme {
  colors: Record<string, string | Record<string, string>>
  spacing: Record<string, string>
  fontSize: Record<string, [string, { lineHeight: string }]>
  fontFamily: Record<string, string[]>
  screens: Record<string, string>
  borderRadius: Record<string, string>
  boxShadow: Record<string, string>
  extend?: Partial<Omit<Theme, 'extend'>>
}

Variants (40+ built-in)

responsive, hover, focus, active, disabled, dark, group, peer,
before, after, marker, first, last, odd, even, first-of-type,
last-of-type, visited, checked, focus-within, focus-visible,
placeholder, selection, file, required, valid, invalid, read-only,
autofill, open, closed, empty, enabled, only, target, indeterminate,
default, optional, print, rtl, ltr, motion-safe, motion-reduce,
contrast-more, contrast-less

Parsed Class Structure

interface ParsedClass {
  raw: string              // Original class string
  variants: string[]       // Applied variants (hover, focus, etc.)
  utility: string          // Core utility name
  value?: string           // Arbitrary value if present
  important: boolean       // Has ! prefix
  arbitrary: boolean       // Uses [] brackets
  typeHint?: string        // Type hint for arbitrary values
}

Usage in Templates

<div class="flex items-center justify-between p-4 bg-white rounded-lg shadow">
  <h1 class="text-2xl font-bold text-gray-900">Title</h1>
  <button class="px-4 py-2 bg-blue-500 text-white rounded hover:bg-blue-600">
    Click me
  </button>
</div>

<!-- Arbitrary values -->
<div class="text-[#1a1a1a] w-[calc(100%-2rem)] grid-cols-[1fr_2fr]">

<!-- Dark mode -->
<div class="bg-white dark:bg-gray-900 text-black dark:text-white">

<!-- Responsive -->
<div class="w-full md:w-1/2 lg:w-1/3">

Built-in Utility Categories

• Display (flex, grid, block, hidden, container)
• Flexbox (direction, wrap, justify, align, gap)
• Spacing (margin, padding)
• Sizing (width, height, min/max)
• Typography (font-size, font-weight, line-height, text-align, text-color)
• Colors (background, text, border, ring)
• Borders (width, radius, style)
• Effects (shadow, opacity)
• Transitions & animations

Gotchas

• Not Tailwind — Crosswind is a separate implementation with Tailwind-compatible syntax
• Stacks uses Crosswind config — config/ui.ts defines Crosswind options which feed Crosswind
• Output is per-page, content-hashed — storage/framework/stx/cache/cw-<hash>.css, generated on demand rather than one bundled stylesheet. The directory is gitignored and safe to delete; the next request regenerates it
• Bun plugin available — can be used as a Bun build plugin for automatic CSS generation
• Attributify mode — optional mode where utilities can be written as HTML attributes instead of classes
• Bracket syntax — text-[#custom] for arbitrary values, same as Tailwind JIT
• Custom rules — defined as [RegExp, (match) => Record<string, string>] tuples
• Presets — extensible via presets for shared configurations