background-position: _pct_pos(x, w, sheet.w) _pct_pos(y, h, sheet.h)
background-image: url((sheet['image']))
background-size: unit(sheet['w'] / w * 100, '%') auto
+ background-repeat: no-repeat
padding-top: unit(h / w * 100, '%')
selector_hover_before = selector + ":hover:before"
if args.hover