Map styles are often defined using SLD, or Style Layer Descriptor documents. These XML documents are very long, verbose and complex to maintain. Amanzi:SLD is a simpler DSL designed to generate SLD documents, but using a very much simpler syntax. Many common cases might be a single line only, while the simplest SLD is usually a dozen lines or more.
Gemfile gem 'amanzi-sld', '~> 0.0.1'
install gem install amanzi-sld