config.rb

// Syntax
preferred_syntax = :scss

// Paths
http_path = "/"
images_dir = "/img"
javascripts_dir = "/js"
sass_dir = "/css/scss/"
css_dir = "/css/"

if environment == :development
    line_comments = true
    output_style = :nested
    sass_options = {:debug_info => true}
end

if environment == :production
    line_comments = false
    output_style = :compressed
    sass_options = {:debug_info => false}

    require 'fileutils'
        on_stylesheet_saved do |file|
            if File.exists?(file)
            filename = File.basename(file, File.extname(file))
            File.rename(file, "css" + "/" + filename + ".min" + File.extname(file))
        end
    end
end 

watch.bat

START compass watch -c config.rb -e development
START compass watch -c config.rb -e production
EXIT

Estrutura de arquivo

<project folder>/    
    CSS/
        SCSS/
            style.scss
        style.css
        style.min.css
    IMG/
    JS/
    config.rb
    watch.bat