class Middleman::Builder

def prerender_css
  logger.debug '== Prerendering CSS'
  css_files = @app.sitemap.resources.select do |resource|
    resource.ext == '.css'
  end.each(&method(:output_resource))
  logger.debug '== Checking for Compass sprites'
  # Double-check for compass sprites
  @app.files.find_new_files!
  @app.sitemap.ensure_resource_list_updated!
  css_files
end