!default_box_shadow_color = #333
 !default_box_shadow_x_offset = 1px
 !default_box_shadow_y_offset = 1px
 !default_box_shadow_blur_radius = 8px
 
 =box-shadow(!color = !default_box_shadow_color, !x_offset = !default_box_shadow_x_offset, !y_offset = !default_box_shadow_y_offset, !blur_radius = !default_box_shadow_blur_radius)
   box-shadow= !x_offset !y_offset !blur_radius !color
   -webkit-box-shadow= !x_offset !y_offset !blur_radius !color
   -moz-box-shadow= !x_offset !y_offset !blur_radius !color