transition($value)
  -webkit-transition $value; /* Saf3.2+, Chrome */
  -moz-transition $value; /* FF4+ */
  -ms-transition $value;
  -o-transition $value; /* Opera 10.5+ */
  transition $value;

default($key, $value)
  if lookup($key) is null
    return $value

  return lookup($key)