Shoes.app :width => 600, :height => 400 do
  flow :width => 400, :height => 400, :margin => 20 do    
    
    fill    '#dfd'
    stroke  '#ddd'
    rect    0, 0, 200, 200
    background white

  end
  background black
end

# in this case draws a window with a black background, then a white flow WITHOUT any sign of the rectangle!