GrooCSS - code CSS in Groovy
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Like Less but without inventing a new language.

GrooCSS lets you code your CSS in Groovy, using a natural Groovy DSL.

It was created by Adam L. Davis (@adamldavis) and inspired by the many other Groovy-based projects out there, like Gradle, Grails, Spock, Ratpack, and grooscript.

  • DSL similar to CSS but with camel-case and some modifications to make it valid Groovy.
  • Keyframes, media, charset, and font-face support.
  • Automatically adds -webkit, -ms, -moz, -o extensions! (configurable)
  • Color support with rgb, rgba, hex, named colors, and several color changing methods (mix, tint, shade, saturate, etc.)
  • Minimization (compress)
  • Support for transforms directly (transformX, etc),
  • Math functions (sqrt, sin, cos, toRadians, etc.) and built-in Measurement math.
  • Unit methods (unit, getUnit, convert)
  • Ability to extend style-groups and add internal groups.
  • Pseudo-classes in DSL (nthChild, etc.)
  • Multiple ways to configure: Config.builder() or using withConfig
  • Close to CSS syntax using getAt, putAt, operator-overloading, underscore, methodMissing, and propertyMissing
  • Translator to convert from existing CSS.
  • Available pretty print (using Config)
  • Ability to create and reuse groups of styles using styles{} syntax.
  • Methods for getting an image's width, height, or size.

New in 0.7 - 0.11.1

  • Better pseudo-class support with %
  • Measurements are now fully supported including math between different compatible types.
  • Added Gradle Plugin
  • Some measurement values are validated (for example, passing 10.deg to maxWidth will throw an AssertionError).
  • New "styles" method for created unattached styles (re: issue #3)
  • Added varieties of convert and process that take String, In/OutputStreams, and Reader/PrintWriter (re: issue #2)
  • Added limited support for using spaces and ~ syntax in Selector definition (limited to two elements)
  • Added mix, tint, shade, and greyscale methods.
  • Added saturate, desaturate, fadein, fadeout, fade, and hue, saturation and brightness methods.
  • Added many colors methods: rgba, hsl, hsla, lighten, darken, etc.
  • Added option (convertUnderline) to convert all underlines in style-classes to dashes.
  • Added ability to use three or more element selectors without xor.
  • Added ability to configure to use some element names as style-classes just in case you need "main" for example to be used as a style-class.
  • Added imports, raw, and comment (ability to import file/reader/stream with parameters; and ability to include comments for output)
  • Gradle GroocssTask now extends Copy task and supports -t option (requires Gradle 4)

Using Gradle with Plugin

Using Gradle 2.1 or later, you simply apply the plugin, provide any optional configuration, and provide a list of files to convert. The plugin adds a convertCss task for converting your groocss files into css. For example:

plugins {
  id "org.groocss.groocss-gradle-plugin" version "0.11.1"
def cssDir = "$parent.buildDir/../www/css"

groocss { // any config
    addOpera = false
    prettyPrint = true
groocssfiles { // a list of in/out files
    index {
        inFile = file('index.groocss')
        outFile = file("$cssDir/index.css")

If you have a lot of files, inFile and outFile can be directories (it will assume groocss files end in .groocss).

There's also a GroocssTask available if you want to have finer-grained control. Here's an example using a task:

task css(type: org.groocss.GroocssTask) {
    conf = new org.groocss.Config(compress: true, addOpera: false)
    from "$rootDir/gcss"
    from "styles"
    into "$cssDir/min"

This also allows the "-t" continuous build option to be used (requires Gradle 4).

Using Gradle without Plugin

import org.groocss.GrooCSS

buildscript {
    repositories { jcenter() }
    dependencies { classpath 'org.groocss:groocss:0.11' }
task css << {
    def file = file('css/out.css')
    GrooCSS.process {
        // DSL goes here


Imports, Raw, and Comment

The ability to import other groocss files is supported by importFile, importStream, and importString methods which take a parameter map and input. For example:

importFile otherCss.absoluteFile, linkColor: '#456789'

This would allow you to make a "template file" for example with variables replaced in multiple ways.

There are also "raw" and "comment" commands, for including raw CSS and comments respectively.

Using convert methods

import org.groocss.GrooCSS

GrooCSS.convertFile('infile.groocss', 'outfile.css')
GrooCSS.convert(new File('in'), new File('out'))

Styles DSL

def myColor = c('#fe33ac') {
  color myColor
  borderColor '#fdcdea'
} ^ div {
  boxShadow '0 0 5px rgba(0, 0, 0, 0.3)'
table {
    color myColor
table.myClass {
    color myColor.darker()
input['class$="test"'] = {
    background yellow
sg '#formId', {     // sg useful for ID's
    minWidth 100.px // resolves to 100px
p + div {
    border '1px solid black'
} | { color red } // | => ,
p >> a { color blue }       //>> => >
p * a { color blue }        // * => *
p - a { color blue }        // - => ~(tilde)
p ^ a { color blue }        // ^ =>  (space)

Measurement Math

def myWidth = + // converts to pt
def myDelay = + 1.s     // converts to ms
def mySize = myWidth / 2    // you can multiply/divide with any number
def doubleSize = myWidth * 2


_.warn { color red }
_.error {
    extend(_.warn) // extend '.warn' also works
    background black


.warn,.error {color: Red;}
.error {background: Black;}


a {
    color '#000'
    add ':hover', { color blue }
div {
    add '> p', { color '#eee' }


a { color: #000; }
a:hover { color: Blue; }
div > p { color: #eee; }

Keyframes and Transforms DSL

def css = GrooCSS.process(new Config(addWebkit: false, addMoz: false, addOpera: false)) {

    keyframes('bounce') {
        40 % {
        60 % {
        frame([0,20,50,80,100]) {


@keyframes bounce {
40%{transform: translateY(-30px);}
60%{transform: translateY(-15px);}
0%, 20%, 50%, 80%, 100%{transform: translateY(0);}


Use the "c", "clr", "rgb" or "rgba" methods to create a color. For example:

def css = GrooCSS.process {
    def sea = c('5512ab') //OR rgb(85, 18, 171)
    _.sea {
        color sea.darker()
        background sea.brighter()
        border "5px solid ${sea.alpha(0.5)}"

You can also use named colors: {
    color darkBlue
    background aliceBlue


fontFace {
    fontFamily 'myFirstFont'
    fontWeight 'normal'
    src 'url(sensational.woff)'

Resolves to:

@font-face { font-family: myFirstFont; font-weight: normal; src:url(sensational.woff); }

Custom styles

body {
	add style('-webkit-touch-callout', 'none')
	add style('-webkit-textSize-adjust', 'none')
	add style('-webkit-user-select', 'none')

Compressing (Minimization)

To "compress" the output (no new-lines), just pass in a Config object:

GrooCSS.process(new Config(compress: true))
GrooCSS.convert(new Config(compress: true), infile, outfile)
groocss { compress = true } // using Gradle plugin


media 'screen', {
    body { width '100%' }


@media screen {
    body { width: 100%; }


input % hover { color blue }
li % nthChild('3n') { color blue }


input:hover { color: Blue; }
li:nth-child(3n) { color: Blue; }


There are three different ways to configure GrooCSS:

  • Using the groovy constructor: new Config(compress: true)
  • Using the builder syntax: Config.builder().compress(true).build()
  • Using the DSL: GrooCSS.withConfig { noExts().compress().utf8() }.process {}

Of these options, the third is most recommended. With the DSL there are several chainable methods available to easily configure your CSS:

  • noExts() - sets all extension flags to false (addOpera, etc.)
  • onlyMs(), onlyWebkit(), etc. - sets all extensions flags to false except one.
  • utf8() - sets the charset to UTF-8.
  • compress() - sets compress flag to true.

Converting from CSS

You can use the Translator to convert existing CSS into GrooCSS syntax:

GrooCSS.convertFromCSS(File inFile, File outFile)

This allows you to get started quickly with GrooCSS in existing projects.